Android(安卓)自定义ContentProvider简单实例

Android 自定义ContentProvider简单实例

Android允许我们定义自己的的ContentProvider对象来共享数据，练练手，简单来实现一下。

要使用ContentProvider来操作数据，必须要有保存数据的场所。可以使用文件或SQLite数据库的方式来保存数据，通常使用SQLite数据库。

1，创建一个数据库帮助类，归根结底都是它在操作数据库。代码如下：

package com.njue;  import android.content.Context; import android.database.sqlite.SQLiteDatabase; import android.database.sqlite.SQLiteDatabase.CursorFactory; import android.database.sqlite.SQLiteOpenHelper;  public class DBManager extends SQLiteOpenHelper { public static final String myProvider_table_name="myProvider_table_name"; String sql="create table myProvider_table_name(id integer,name text)";   public DBManager(Context context) {     super(context, "myPrivoder.db", null, 1);     // TODO Auto-generated constructor stub   }    @Override   public void onCreate(SQLiteDatabase arg0) {     // TODO Auto-generated method stub    arg0.execSQL(sql);   }    @Override   public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {     // TODO Auto-generated method stub    }  }

2，创建一个myProvider类，该类继承ContentProvider，实现其抽象方法来操作数据库，该类引用DBManager类来获得数据库实例。

package com.njue;  import android.content.ContentProvider; import android.content.ContentValues; import android.database.Cursor; import android.database.sqlite.SQLiteDatabase; import android.net.Uri;  public class myProvider extends ContentProvider {   DBManager dbHelper;   @Override   public int delete(Uri arg0, String arg1, String[] arg2) {     // TODO Auto-generated method stub     SQLiteDatabase db=dbHelper.getWritableDatabase();     int id=db.delete(DBManager.myProvider_table_name, arg1, arg2);     if(id!=0)return id;     return 0;   }    @Override   public String getType(Uri uri) {     // TODO Auto-generated method stub     return null;   }    @Override   public Uri insert(Uri uri, ContentValues values) {     // TODO Auto-generated method stub     SQLiteDatabase db=dbHelper.getWritableDatabase();     db.insert(DBManager.myProvider_table_name, "id", values);     return null;   }    @Override   public boolean onCreate() {     // TODO Auto-generated method stub     dbHelper=new DBManager(getContext());     return true;   }    @Override   public Cursor query(Uri uri, String[] projection, String selection,       String[] selectionArgs, String sortOrder) {     // TODO Auto-generated method stub     SQLiteDatabase db=dbHelper.getWritableDatabase();     Cursor c=db.query(DBManager.myProvider_table_name,projection, selection, selectionArgs, null, null, sortOrder);     return c;   }    @Override   public int update(Uri uri, ContentValues values, String selection,       String[] selectionArgs) {     // TODO Auto-generated method stub     SQLiteDatabase db=dbHelper.getWritableDatabase();     int id=db.update(DBManager.myProvider_table_name, values, selection, selectionArgs);     if(id!=0)return id;     return 0;   }  }

3，ContextProvider必须声明才能使用，因此，需要在AndroidManifest.xml配置文件中声明。声明很简单，需要类名称和授权名称两个属性。

到这里，我们自定义的ContentProvider就完成了。我们可以在Eclipse中的File Explorer 窗口中看到自定义的ContentProvider

4，简单测试

package com.njue;  import android.app.Activity; import android.content.ContentResolver; import android.content.ContentValues; import android.database.Cursor; import android.net.Uri; import android.os.Bundle; import android.util.Log; import android.view.View; import android.widget.Button; import android.widget.EditText; import android.widget.TextView;  public class Content_providerActivity extends Activity {   /** Called when the activity is first created. */    Uri uri;    String AUTHORITY="content://com.njue.myProvider/myProvider_table_name";    ContentResolver cr;    EditText input;    Button insert;    TextView show;   @Override   public void onCreate(Bundle savedInstanceState) {     super.onCreate(savedInstanceState);     setContentView(R.layout.main);     input=(EditText)findViewById(R.id.input);     insert=(Button)findViewById(R.id.insert);     show=(TextView)findViewById(R.id.show);     uri=uri.parse(AUTHORITY);     cr=this.getContentResolver();     insert.setOnClickListener(new Button.OnClickListener(){        @Override       public void onClick(View v) {         // TODO Auto-generated method stub          ContentValues values=new ContentValues();           values.put("name", input.getText().toString());           cr.insert(uri, values);           Cursor c=cr.query(uri, null, null, null, null);           show.setText("");           c.moveToFirst();           while(c.moveToNext()){            show.append(c.getString(1)+"\r\n");           }           input.setText("");       }});        } }

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