在Google Maps Android(SQLite)中添加和保存标记

Question

我对应用程序有一点问题，想寻求帮助。代码中没有错误，但是我在设备和模拟器上显示一条消息"应用程序已停止"。从日志中，我意识到方法setOnMapClickListener中的错误。我的任务 - 向数据库添加标记，然后在应用程序完全关闭然后启动后 - 显示数据库中的标记。不明白，为什么这个功能不起作用，我想在我的应用程序的这一部分了解这个主题。提前感谢任何帮助！附言没有方法设置地图点击监听器，插入任务，绘制点应用程序正常启动。

位置数据库.java

package com.morgannik.navigatortransportapp;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
public class LocationsDB extends SQLiteOpenHelper{
    /** Database name */
    private static String DBNAME = "locationmarkersqlite";
    /** Version number of the database */
    private static int VERSION = 1;
    /** Primary key */
    public static final String FIELD_ROW_ID = "_id";
    /** Latitude */
    public static final String FIELD_LAT = "lat";
    /** Longitude*/
    public static final String FIELD_LNG = "lng";
    /** Table locations, stores the zoom level of map*/
    public static final String FIELD_ZOOM = "zom";
    /** Table name */
    private static final String DATABASE_TABLE = "locations";
    /** An instance variable for SQLiteDatabase */
    private SQLiteDatabase mDB;
    /** Constructor */
    public LocationsDB(Context context) {
        super(context, DBNAME, null, VERSION);
        this.mDB = getWritableDatabase();
    }
    /** This is a callback method, invoked when the method getReadableDatabase() / getWritableDatabase() is called
     * provided the database does not exists
     * */
    @Override
    public void onCreate(SQLiteDatabase db) {
        String sql =     "create table " + DATABASE_TABLE + " ( " +
                FIELD_ROW_ID + " integer primary key autoincrement , " +
                FIELD_LNG + " double , " +
                FIELD_LAT + " double , " +
                FIELD_ZOOM + " text " +
                " ) ";
        db.execSQL(sql);
    }
    /** Inserts a new location to the table locations */
    public long insert(ContentValues contentValues){
        long rowID = mDB.insert(DATABASE_TABLE, null, contentValues);
        return rowID;
    }
    /** Deletes all locations from the table */
    public int del(){
        int cnt = mDB.delete(DATABASE_TABLE, null , null);
        return cnt;
    }
    /** Returns all the locations from the table */
    public Cursor getAllLocations(){
        return mDB.query(DATABASE_TABLE, new String[] { FIELD_ROW_ID,  FIELD_LAT , FIELD_LNG, FIELD_ZOOM } , null, null, null, null, null);
    }
    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    }
}

LocationsContentProvider.java

package com.morgannik.navigatortransportapp;
import android.content.ContentProvider;
import android.content.ContentUris;
import android.content.ContentValues;
import android.content.UriMatcher;
import android.database.Cursor;
import android.net.Uri;
import java.sql.SQLException;
/** A custom Content Provider to do the database operations */
public class LocationsContentProvider extends ContentProvider{
    public static final String PROVIDER_NAME = "com.morgannik.navigatortransportapp.locations";
    /** A uri to do operations on locations table. A content provider is identified by its uri */
    public static final Uri CONTENT_URI = Uri.parse("content://" + PROVIDER_NAME + "/locations" );
    /** Constant to identify the requested operation */
    private static final int LOCATIONS = 1;
    private static final UriMatcher uriMatcher ;
    static {
        uriMatcher = new UriMatcher(UriMatcher.NO_MATCH);
        uriMatcher.addURI(PROVIDER_NAME, "locations", LOCATIONS);
    }
    /** This content provider does the database operations by this object */
    LocationsDB mLocationsDB;
    /** A callback method which is invoked when the content provider is starting up */
    @Override
    public boolean onCreate() {
        mLocationsDB = new LocationsDB(getContext());
        return true;
    }
    /** A callback method which is invoked when insert operation is requested on this content provider */
    @Override
    public Uri insert(Uri uri, ContentValues values) {
        long rowID = mLocationsDB.insert(values);
        Uri _uri=null;
        if(rowID>0){
            _uri = ContentUris.withAppendedId(CONTENT_URI, rowID);
        }else {
            try {
                throw new SQLException("Failed to insert : " + uri);
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        return _uri;
    }
    @Override
    public int update(Uri uri, ContentValues values, String selection,
                      String[] selectionArgs) {
        // TODO Auto-generated method stub
        return 0;
    }

    /** A callback method which is invoked when delete operation is requested on this content provider */
    @Override
    public int delete(Uri uri, String selection, String[] selectionArgs) {
        int cnt = 0;
        cnt = mLocationsDB.del();
        return cnt;
    }
    /** A callback method which is invoked by default content uri */
    @Override
    public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) {
        if(uriMatcher.match(uri)==LOCATIONS){
            return mLocationsDB.getAllLocations();
        }
        return null;
    }

    @Override
    public String getType(Uri uri) {
        return null;
    }
}

地图活动.java

package com.morgannik.navigatortransportapp;
import android.content.ContentValues;
import android.os.Bundle;
import android.support.v4.app.FragmentActivity;
import android.view.View;
import android.widget.Toast;
import com.google.android.gms.maps.CameraUpdateFactory;
import com.google.android.gms.maps.GoogleMap;
import com.google.android.gms.maps.GoogleMap.OnMapClickListener;
import com.google.android.gms.maps.GoogleMap.OnMapLongClickListener;
import com.google.android.gms.maps.OnMapReadyCallback;
import com.google.android.gms.maps.SupportMapFragment;
import com.google.android.gms.maps.model.BitmapDescriptorFactory;
import com.google.android.gms.maps.model.LatLng;
import com.google.android.gms.maps.model.MarkerOptions;
import com.squareup.okhttp.OkHttpClient;
import com.squareup.okhttp.Request;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.TimeUnit;
public class MapsActivity extends FragmentActivity implements OnMapReadyCallback {
    private GoogleMap mMap;
    public void onClickAdd(View view) {
        mMap.addMarker(new MarkerOptions().position(new LatLng(47.23135, 39.72328)).draggable(true).icon(
                BitmapDescriptorFactory
                        .defaultMarker(BitmapDescriptorFactory.HUE_GREEN)));
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_maps);
        // Obtain the SupportMapFragment and get notified when the map is ready to be used.
        SupportMapFragment mapFragment = (SupportMapFragment)
                getSupportFragmentManager().findFragmentById(R.id.map);
        mapFragment.getMapAsync(this);
        mMap.setOnMapClickListener(new OnMapClickListener() {
            @Override
            public void onMapClick(LatLng point) {

                // Drawing marker on the map
                drawMarker(point);
                // Creating an instance of ContentValues
                ContentValues contentValues = new ContentValues();
                // Setting latitude in ContentValues
                contentValues.put(LocationsDB.FIELD_LAT, point.latitude );
                // Setting longitude in ContentValues
                contentValues.put(LocationsDB.FIELD_LNG, point.longitude);
                // Setting zoom in ContentValues
                contentValues.put(LocationsDB.FIELD_ZOOM, mMap.getCameraPosition().zoom);
                // Creating an instance of LocationInsertTask
                LocationInsertTask insertTask = new LocationInsertTask();
                // Storing the latitude, longitude and zoom level to SQLite database
                insertTask.execute(contentValues);
                Toast.makeText(getBaseContext(), "Marker is added to the Map", Toast.LENGTH_SHORT).show();
            }
        });

        mMap.setOnMapLongClickListener(new OnMapLongClickListener() {
            @Override
            public void onMapLongClick(LatLng point) {
                // Removing all markers from the Google Map
                mMap.clear();
                // Creating an instance of LocationDeleteTask
                LocationDeleteTask deleteTask = new LocationDeleteTask();
                // Deleting all the rows from SQLite database table
                deleteTask.execute();
                Toast.makeText(getBaseContext(), "All markers are removed", Toast.LENGTH_LONG).show();
            }
        });
    }

    private void drawMarker(LatLng point){
        // Creating an instance of MarkerOptions
        MarkerOptions markerOptions = new MarkerOptions();
        // Setting latitude and longitude for the marker
        markerOptions.position(point);
        // Adding marker on the Google Map
        mMap.addMarker(markerOptions);
    }
    private class LocationInsertTask extends android.os.AsyncTask<ContentValues, Void, Void> {
        @Override
        protected Void doInBackground(ContentValues... contentValues) {
            /** Setting up values to insert the clicked location into SQLite database */
            getContentResolver().insert(LocationsContentProvider.CONTENT_URI, contentValues[0]);
            return null;
        }
    }
    private class LocationDeleteTask extends android.os.AsyncTask<Void, Void, Void> {
        @Override
        protected Void doInBackground(Void... params) {
            /** Deleting all the locations stored in SQLite database */
            getContentResolver().delete(LocationsContentProvider.CONTENT_URI, null, null);
            return null;
        }
    }
    @Override
    public void onMapReady(GoogleMap googleMap) {
        mMap = googleMap;
        LatLng rostov = new LatLng(47.23135, 39.72328);
        /*mMap.addMarker(new MarkerOptions().position(rostov).title("Rostov-on-Don").icon(
                        BitmapDescriptorFactory.defaultMarker(BitmapDescriptorFactory.HUE_CYAN)
                )
        );*/
        mMap.moveCamera(CameraUpdateFactory.newLatLngZoom(rostov, 14.f));
    }
}

Build.grandle

apply plugin: 'com.android.application'
android {
    compileSdkVersion 26
    defaultConfig {
        applicationId "com.morgannik.navigatortransportapp"
        minSdkVersion 19
        targetSdkVersion 26
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}
dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation 'com.android.support:appcompat-v7:26.1.0'
    implementation 'com.google.android.gms:play-services-maps:11.8.0'
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'com.android.support.test:runner:1.0.1'
    androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.1'
    compile 'com.squareup.okhttp:okhttp:2.7.0'
    compile 'com.squareup.okio:okio:1.6.0'
}

安卓清单

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.morgannik.navigatortransportapp">
    <!--
         The ACCESS_COARSE/FINE_LOCATION permissions are not required to use
         Google Maps Android API v2, but you must specify either coarse or fine
         location permissions for the 'MyLocation' functionality. 
    -->
    <permission
        android:name="com.morgannik.navigatortransportapp.permission.MAPS_RECEIVE"
        android:protectionLevel="signature"/>
    <uses-permission android:name="com.morgannik.navigatortransportapp.permission.MAPS_RECEIVE"/>
    <uses-permission android:name="android.permission.INTERNET" />
    <uses-permission android:name="android.permission.ACCESS_INTERNET" />
    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
    <uses-permission android:name="com.google.android.providers.gsf.permission.READ_GSERVICES" />
    <uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
    <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
    <uses-feature
        android:glEsVersion="0x00020000"
        android:required="true"/>
    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <!--
             The API key for Google Maps-based APIs is defined as a string resource.
             (See the file "res/values/google_maps_api.xml").
             Note that the API key is linked to the encryption key used to sign the APK.
             You need a different API key for each encryption key, including the release key that is used to
             sign the APK for publishing.
             You can define the keys for the debug and release targets in src/debug/ and src/release/. 
        -->
        <meta-data
            android:name="com.google.android.geo.API_KEY"
            android:value="@string/google_maps_key" />
        <activity
            android:name=".MapsActivity"
            android:label="@string/title_activity_maps">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <provider
            android:name="LocationsContentProvider"
            android:authorities="com.morgannik.navigatortransportapp.locations"
            android:exported="false" />
    </application>
</manifest>

activity_maps.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">
    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:onClick="onClickAdd"
        android:text="Add" />
    <fragment xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:map="http://schemas.android.com/apk/res-auto"
        xmlns:tools="http://schemas.android.com/tools"
        android:id="@+id/map"
        android:name="com.google.android.gms.maps.SupportMapFragment"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        tools:context="com.morgannik.navigatortransportapp.MapsActivity" />
</LinearLayout>

Answer 1

我们需要等待映射准备就绪，然后分配变量 mMap 放出像 setOnMapClickListener 这样的方法。

MapsActivity 类的来源：

package com.morgannik.navigatortransportapp;
import android.content.ContentValues;
import android.database.Cursor;
import android.net.Uri;
import android.os.Bundle;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.LoaderManager;
import android.support.v4.content.CursorLoader;
import android.support.v4.content.Loader;
import android.view.View;
import android.widget.Toast;
import com.google.android.gms.maps.CameraUpdateFactory;
import com.google.android.gms.maps.GoogleMap;
import com.google.android.gms.maps.OnMapReadyCallback;
import com.google.android.gms.maps.SupportMapFragment;
import com.google.android.gms.maps.model.BitmapDescriptorFactory;
import com.google.android.gms.maps.model.LatLng;
import com.google.android.gms.maps.model.MarkerOptions;
import com.squareup.okhttp.OkHttpClient;
import com.squareup.okhttp.Request;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.TimeUnit;
public class MapsActivity extends FragmentActivity implements OnMapReadyCallback, LoaderManager.LoaderCallbacks<Cursor> {
    private GoogleMap mMap;
    public void onClickAdd(View view)
    {
        mMap.addMarker(new MarkerOptions().position(new LatLng(47.23135, 39.72328)).draggable(true).icon(
                BitmapDescriptorFactory
                        .defaultMarker(BitmapDescriptorFactory.HUE_GREEN)));
    }
    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_maps);
        // Obtain the SupportMapFragment and get notified when the map is ready to be used.
        SupportMapFragment mapFragment = (SupportMapFragment)
                getSupportFragmentManager().findFragmentById(R.id.map);
        mapFragment.getMapAsync(this);
        // Invoke LoaderCallbacks to retrieve and draw already saved locations in map
        getSupportLoaderManager().initLoader(0, null, this);
    }
    private void drawMarker(LatLng point){
        // Creating an instance of MarkerOptions
        MarkerOptions markerOptions = new MarkerOptions();
        // Setting latitude and longitude for the marker
        markerOptions.position(point);
        // Adding marker on the Google Map
        mMap.addMarker(markerOptions);
    }
    private class LocationInsertTask extends android.os.AsyncTask<ContentValues, Void, Void>
    {
        @Override
        protected Void doInBackground(ContentValues... contentValues) {
            /** Setting up values to insert the clicked location into SQLite database */
            getContentResolver().insert(LocationsContentProvider.CONTENT_URI, contentValues[0]);
            return null;
        }
    }
    private class LocationDeleteTask extends android.os.AsyncTask<Void, Void, Void>
    {
        @Override
        protected Void doInBackground(Void... params)
        {
            /** Deleting all the locations stored in SQLite database */
            getContentResolver().delete(LocationsContentProvider.CONTENT_URI, null, null);
            return null;
        }
    }

    @Override
    public Loader<Cursor> onCreateLoader(int arg0,
                                         Bundle arg1)
    {
        // Uri to the content provider LocationsContentProvider
        Uri uri = LocationsContentProvider.CONTENT_URI;
        // Fetches all the rows from locations table
        return new CursorLoader(this, uri, null, null, null, null);
    }

    @Override
    public void onLoadFinished(Loader<Cursor> arg0,
                               Cursor arg1)
    {
        int locationCount = 0;
        double lat=0;
        double lng=0;
        float zoom=0;
        // Number of locations available in the SQLite database table
        locationCount = arg1.getCount();
        // Move the current record pointer to the first row of the table
        arg1.moveToFirst();
        for(int i=0;i<locationCount;i++)
        {
            // Get the latitude
            lat = arg1.getDouble(arg1.getColumnIndex(LocationsDB.FIELD_LAT));
            // Get the longitude
            lng = arg1.getDouble(arg1.getColumnIndex(LocationsDB.FIELD_LNG));
            // Get the zoom level
            zoom = arg1.getFloat(arg1.getColumnIndex(LocationsDB.FIELD_ZOOM));
            // Creating an instance of LatLng to plot the location in Google Maps
            LatLng location = new LatLng(lat, lng);
            // Drawing the marker in the Google Maps
            drawMarker(location);
            // Traverse the pointer to the next row
            arg1.moveToNext();
        }
        if(locationCount>0)
        {
            // Moving CameraPosition to last clicked position
            mMap.moveCamera(CameraUpdateFactory.newLatLng(new LatLng(lat,lng)));
            // Setting the zoom level in the map on last position  is clicked
            mMap.animateCamera(CameraUpdateFactory.zoomTo(zoom));
        }
    }
    @Override
    public void onLoaderReset(Loader<Cursor> arg0)
    {
        // TODO Auto-generated method stub
    }
    @Override
    public void onMapReady(GoogleMap googleMap)
    {
        mMap = googleMap;
        mMap.setOnMapClickListener(new GoogleMap.OnMapClickListener()
        {
            @Override
            public void onMapClick(LatLng point)
            {

                // Drawing marker on the map
                drawMarker(point);
                // Creating an instance of ContentValues
                ContentValues contentValues = new ContentValues();
                // Setting latitude in ContentValues
                contentValues.put(LocationsDB.FIELD_LAT, point.latitude );
                // Setting longitude in ContentValues
                contentValues.put(LocationsDB.FIELD_LNG, point.longitude);
                // Setting zoom in ContentValues
                contentValues.put(LocationsDB.FIELD_ZOOM, mMap.getCameraPosition().zoom);
                // Creating an instance of LocationInsertTask
                LocationInsertTask insertTask = new LocationInsertTask();
                // Storing the latitude, longitude and zoom level to SQLite database
                insertTask.execute(contentValues);
                Toast.makeText(getBaseContext(), "Marker is added to the Map", Toast.LENGTH_SHORT).show();
            }
        });

        mMap.setOnMapLongClickListener(new GoogleMap.OnMapLongClickListener()
        {
            @Override
            public void onMapLongClick(LatLng point)
            {
                // Removing all markers from the Google Map
                mMap.clear();
                // Creating an instance of LocationDeleteTask
                LocationDeleteTask deleteTask = new LocationDeleteTask();
                // Deleting all the rows from SQLite database table
                deleteTask.execute();
                Toast.makeText(getBaseContext(), "All markers are removed", Toast.LENGTH_LONG).show();
            }
        });
        LatLng rostov = new LatLng(47.23135, 39.72328);
        /*mMap.addMarker(new MarkerOptions().position(rostov).title("Rostov-on-Don").icon(
                        BitmapDescriptorFactory.defaultMarker(BitmapDescriptorFactory.HUE_CYAN)
                )
        );*/
        mMap.moveCamera(CameraUpdateFactory.newLatLngZoom(rostov, 14.f));
    }
}