遵循本教程以读取资产文件夹的图像。在这里,链接链接到资产文件夹读取图像的链接ContentClass从Content -Provider延伸,但我在第一行中遇到错误。此错误在很第一行ContentClass1行上。请让我知道我需要在ContentClass1.java
中实现哪些内容。Multiple markers at this line
- The type Contentclass1 must implement the inherited abstract method ContentProvider.onCreate()
- The type Contentclass1 must implement the inherited abstract method ContentProvider.delete(Uri, String, String[])
- The type Contentclass1 must implement the inherited abstract method ContentProvider.query(Uri, String[], String, String[],
String)
- The type Contentclass1 must implement the inherited abstract method ContentProvider.getType(Uri)
- The type Contentclass1 must implement the inherited abstract method ContentProvider.update(Uri, ContentValues, String,
String[])
- The type Contentclass1 must implement the inherited abstract method ContentProvider.insert(Uri, ContentValues)
contentclass1.java
package com.example.shareima;
import java.io.FileNotFoundException;
import java.io.IOException;
import android.content.ContentProvider;
import android.content.res.AssetFileDescriptor;
import android.content.res.AssetManager;
import android.net.Uri;
public class Contentclass1 extends ContentProvider
{
@Override
public AssetFileDescriptor openAssetFile(Uri uri,String mode) throws FileNotFoundException {
AssetManager am = getContext().getAssets();
String file_name = uri.getLastPathSegment();
if(file_name == null)
throw new FileNotFoundException();
AssetFileDescriptor afd = null;
try {
afd = am.openFd(file_name);
} catch (IOException e) {
e.printStackTrace();
}
return afd;//super.openAssetFile(uri, mode);
}
}
subest.xml
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.shareima"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="12"
android:targetSdkVersion="17" />
<uses-permission android:name="android.permission.INTERNET"/>
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name="com.example.shareima.MainActivity"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN"/>
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<provider android:name=".Contentclass1"
android:authorities="com.example.shareima"/>
</application>
</manifest>
ContentProvider是一个抽象类。这意味着它具有某些方法的定义,但没有为其提供实现。因此,当您扩展ContentProvider时,您需要在类中提供这些方法的实现(即使您无意在代码中调用它们)。这是教程说"为所需的抽象方法实现存根"以及您的编译错误所指的内容时的含义。
您可以通过在类中添加以下内容来实现它们:
@Override
public int delete(Uri arg0, String arg1, String[] arg2) {
return 0;
}
@Override
public String getType(Uri arg0) {
return null;
}
@Override
public Uri insert(Uri arg0, ContentValues arg1) {
return null;
}
@Override
public boolean onCreate() {
return false;
}
@Override
public Cursor query(Uri arg0, String[] arg1, String arg2, String[] arg3, String arg4) {
return null;
}
@Override
public int update(Uri arg0, ContentValues arg1, String arg2, String[] arg3) {
return 0;
}
这些被称为"存根",因为它们不做任何处理(除了返回null/Zero/false值)。