我真的被卡住了，不知道该怎么办。我已经研究了startActivityForResult和内容提供商，但我不知道如何为这个应用程序实现它们中的任何一个。
我不知道如何从数据库中获取数据并使用相同的listview更新displayBottomList，这样我就不必将用户重定向到新的布局/活动。不确定我是否可以调用一个新的查询，并将其设置为不同的游标，然后在它们之间切换。我看过swapCursor，但使用同一个适配器时，它是如何工作的？
我有一个ListView，当用户单击列表中的一行时，我想用web服务调用中的新数据刷新它。我正在使用CursorAdapter。我可以正确地获得该行的数据onClick。
我遇到的问题是，在不将我发送到另一个"活动"的情况下，如何更新listView以使用数据库/响应中的新信息重新填充。我希望用户保持在同一屏幕上，但只使用新数据更新listView。
当onClick在适配器中时，不确定如何让适配器通知适配器更新并填充新的ListView，但ListView正在MainActivity中创建。
BottomListView的适配器，单击一行时我要更新的适配器。
public class BottomListViewAdapter extends CursorAdapter {
private String mEmployeeNumber;
private EmployeeDBHandler dbHandler;
public BottomListViewAdapter(Context context, Cursor cursor) {
super(context, cursor, 0);
}
@Override
public View newView(Context context, Cursor cursor, ViewGroup parent) {
return LayoutInflater.from(context).inflate(R.layout.contact_cardview_layout, parent, false);
}
@Override
public void bindView(View view, final Context context, final Cursor cursor) {
dbHandler = new EmployeeDBHandler(context);
ViewHolder holder;
holder = new ViewHolder();
holder.tvFirstName = (TextView) view.findViewById(R.id.personFirstName);
holder.tvLastName = (TextView) view.findViewById(R.id.personLastName);
holder.tvTitle = (TextView) view.findViewById(R.id.personTitle);
holder.mPeepPic = (ImageView) view.findViewById(R.id.person_photo);
holder.mDetailsButton = (ImageButton) view.findViewById(R.id.fullDetailButton);
holder.mCardView = (CardView) view.findViewById(R.id.home_screen_cardView);
String mFirstName = cursor.getString(cursor.getColumnIndexOrThrow("First_name"));
String mLastName = cursor.getString(cursor.getColumnIndexOrThrow("Last_name"));
String mTitle = cursor.getString(cursor.getColumnIndexOrThrow("Payroll_title"));
String mThumbnail = cursor.getString(cursor.getColumnIndexOrThrow("ThumbnailData"));
holder.tvFirstName.setText(mFirstName);
holder.tvLastName.setText(mLastName);
holder.tvTitle.setText(mTitle);
if (mThumbnail != null) {
byte[] imageAsBytes = Base64.decode(mThumbnail.getBytes(), Base64.DEFAULT);
Bitmap parsedImage = BitmapFactory.decodeByteArray(imageAsBytes, 0, imageAsBytes.length);
holder.mPeepPic.setImageBitmap(parsedImage);
} else {
holder.mPeepPic.setImageResource(R.drawable.img_place_holder_adapter);
}
final int position = cursor.getPosition();
holder.mDetailsButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
cursor.moveToPosition(position);
String mEmployeeNumber = cursor.getString(1);
String mEmail = cursor.getString(8);
String mFirstName = cursor.getString(2);
String mLastName = cursor.getString(3);
String mPhoneMobile = cursor.getString(4);
String mPhoneOffice = cursor.getString(5);
String mCostCenter = cursor.getString(10);
String mHasDirectReports = cursor.getString(7);
String mTitle = cursor.getString(6);
String mPic = cursor.getString(9);
Intent mIntent = new Intent(context, EmployeeFullInfo.class);
mIntent.putExtra("Employee_number", mEmployeeNumber);
mIntent.putExtra("Email", mEmail);
mIntent.putExtra("First_name", mFirstName);
mIntent.putExtra("Last_name", mLastName);
mIntent.putExtra("Phone_mobile", mPhoneMobile);
mIntent.putExtra("Phone_office", mPhoneOffice);
mIntent.putExtra("Cost_center_id", mCostCenter);
mIntent.putExtra("Has_direct_reports", mHasDirectReports);
mIntent.putExtra("Payroll_title", mTitle);
mIntent.putExtra("ThumbnailData", mPic);
mIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
view.getContext().startActivity(mIntent);
}
});
holder.mCardView.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
cursor.moveToPosition(position);
mEmployeeNumber = cursor.getString(1);
Toast.makeText(context, mEmployeeNumber, Toast.LENGTH_SHORT).show();
callNewDirectReport();
notifyDataSetChanged();
}
});
}
public static class ViewHolder {
TextView tvFirstName;
TextView tvLastName;
TextView tvTitle;
ImageView mPeepPic;
ImageButton mDetailsButton;
CardView mCardView;
}
private void callNewDirectReport() {
String mDirectReportUrl = "mURL";
HttpUrl.Builder urlBuilder = HttpUrl.parse(mDirectReportUrl).newBuilder();
urlBuilder.addQueryParameter("manager_employee_number", mEmployeeNumber);
String url = urlBuilder.build().toString();
OkHttpClient client = getUnsafeOkHttpClient();
Request request = new Request.Builder()
.url(url)
.build();
client.newCall(request).enqueue(new Callback() {
@Override
public void onFailure(Call call, IOException e) {
e.printStackTrace();
}
@Override
public void onResponse(Call call, Response response) throws IOException {
final String responseData = response.body().string();
final InputStream stream = new ByteArrayInputStream(responseData.getBytes());
final XMLPullParserHandler parserHandler = new XMLPullParserHandler();
final ArrayList<Employee> employees = (ArrayList<Employee>) parserHandler.parse(stream);
for (Employee e : employees) {
dbHandler.addEmployee(e);
}
}
});
}
@Override
public void notifyDataSetChanged() {
super.notifyDataSetChanged();
}
}
调用适配器的My MainActivity
public class MainActivity extends AppCompatActivity {
private ProgressBar mProgressBar;
private BottomListViewAdapter mBottomAdapter;
private View mDividerView;
EmployeeDBHandler dbHandler;
private int mStartingEmployeeID = mStartingID;
private String table = "employees";
private static final int LOADER_INTEGER = 1;
private Cursor mBottomCursor, mTopCursor;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mProgressBar = (ProgressBar) findViewById(R.id.progressBar);
mDividerView = findViewById(R.id.divider);
dbHandler = new EmployeeDBHandler(getApplicationContext());
mProgressBar.setVisibility(View.VISIBLE);
mDividerView.setVisibility(View.GONE);
getXMLData();
//GUI for seeing android SQLite Database in Chrome Dev Tools
Stetho.InitializerBuilder inBuilder = Stetho.newInitializerBuilder(this);
inBuilder.enableWebKitInspector(Stetho.defaultInspectorModulesProvider(this));
Stetho.Initializer in = inBuilder.build();
Stetho.initialize(in);
}
public void getXMLData() {
OkHttpClient client = getUnsafeOkHttpClient();
Request request = new Request.Builder()
.url(getString(R.string.API_FULL_URL))
.build();
client.newCall(request).enqueue(new Callback() {
@Override
public void onFailure(Call call, IOException e) {
e.printStackTrace();
}
@Override
public void onResponse(Call call, final Response response) throws IOException {
final String responseData = response.body().string();
final InputStream stream = new ByteArrayInputStream(responseData.getBytes());
final XMLPullParserHandler parserHandler = new XMLPullParserHandler();
final ArrayList<Employee> employees = (ArrayList<Employee>) parserHandler.parse(stream);
for (Employee e : employees) {
dbHandler.addEmployee(e);
}
runOnUiThread(new Runnable() {
@Override
public void run() {
mProgressBar.setVisibility(View.GONE);
mDividerView.setVisibility(View.VISIBLE);
displayTopList();
displayBottomList();
}
});
}
});
}
public void displayTopList() {
SQLiteDatabase db = dbHandler.getWritableDatabase();
mTopCursor = db.rawQuery("SELECT * FROM " + table + " WHERE " + "Employee_number" + "=" + mStartingEmployeeID, null);
ListView mTopListView = (ListView) findViewById(R.id.mTopList);
TopListCursorAdapter topAdapter = new TopListCursorAdapter(this, mTopCursor);
mTopListView.setAdapter(topAdapter);
}
public void displayBottomList() {
SQLiteDatabase db = dbHandler.getWritableDatabase();
mBottomCursor = db.rawQuery("SELECT * FROM " + table + " WHERE " +
"Employee_number" + "!=" + mStartingEmployeeID + " AND " +
"Manager_employee_number" + "=" + mStartingEmployeeID + " ORDER BY " +
"Last_name" + " ASC", null);
ListView mBottomListView = (ListView) findViewById(R.id.mDirectReportList);
mBottomAdapter = new BottomListViewAdapter(this, mBottomCursor);
mBottomListView.setAdapter(mBottomAdapter);
mBottomAdapter.notifyDataSetChanged();
}
}
现在callNewDirectReport()中的代码发出API请求并将结果存储在数据库中。这不会更新适配器以显示新项，而是需要重新查询数据库并获取更新的Cursor。以下是如何做到这一点的示例：
public class BottomListViewAdapter extends CursorAdapter {
private String mEmployeeNumber;
private EmployeeDBHandler dbHandler;
private Activity activityRef;
public BottomListViewAdapter(Context context, Cursor cursor) {
super(context, cursor, 0);
// keep a reference to the activity
activityRef = (Activity) context;
}
//...
private void callNewDirectReport() {
//...
client.newCall(request).enqueue(new Callback() {
@Override
public void onFailure(Call call, IOException e) {
e.printStackTrace();
}
@Override
public void onResponse(Call call, Response response) throws IOException {
final String responseData = response.body().string();
final InputStream stream = new ByteArrayInputStream(responseData.getBytes());
final XMLPullParserHandler parserHandler = new XMLPullParserHandler();
final ArrayList<Employee> employees = (ArrayList<Employee>) parserHandler.parse(stream);
for (Employee e : employees) {
dbHandler.addEmployee(e);
}
// the new items are in the database so requery the database to get a new fresher Cursor:
SQLiteDatabase db = dbHandler.getWritableDatabase();
Cursor fresherCursor = db.rawQuery("SELECT * FROM " + table + " WHERE " +
"Employee_number" + "!=" + mStartingEmployeeID + " AND " +
"Manager_employee_number" + "=" + mStartingEmployeeID + " ORDER BY " +
"Last_name" + " ASC", null);
//change the adapter's Cursor
activityRef.runOnUiThread(new Runnable() {
public void run() {
swapCursor(freshedCursor);
}
});
}
});
}
}
您可以使用startActivityForResult接收来自活动的回调，这里有一个教程来解释如何使用它：https://developer.android.com/training/basics/intents/result.html
当您在onActivityResult中收到回调时，您可以更新数据并调用notifyDatasetChanged。
你不能从另一个活动中调用代码，因为活动是由android处理的。安卓系统可能会杀死你试图调用的活动，并在必要时重新创建它。