Android 自定义ContentProvider
16lz
2021-01-23
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}@Overridepublic void onCreate(SQLiteDatabase arg0) {// TODO Auto-generated method stub arg0.execSQL(sql);}@Overridepublic 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;@Overridepublic int delete(Uri arg0, String arg1, String[] arg2) {// TODO Auto-generated method stubSQLiteDatabase db=dbHelper.getWritableDatabase();int id=db.delete(DBManager.myProvider_table_name, arg1, arg2);if(id!=0)return id;return 0;}@Overridepublic String getType(Uri uri) {// TODO Auto-generated method stubreturn null;}@Overridepublic Uri insert(Uri uri, ContentValues values) {// TODO Auto-generated method stubSQLiteDatabase db=dbHelper.getWritableDatabase();db.insert(DBManager.myProvider_table_name, "id", values);return null;}@Overridepublic boolean onCreate() {// TODO Auto-generated method stubdbHelper=new DBManager(getContext());return true;}@Overridepublic Cursor query(Uri uri, String[] projection, String selection,String[] selectionArgs, String sortOrder) {// TODO Auto-generated method stubSQLiteDatabase db=dbHelper.getWritableDatabase();Cursor c=db.query(DBManager.myProvider_table_name,projection, selection, selectionArgs, null, null, sortOrder);return c;}@Overridepublic int update(Uri uri, ContentValues values, String selection,String[] selectionArgs) {// TODO Auto-generated method stubSQLiteDatabase 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。
<provider android:name="myProvider"android:authorities="com.njue.myProvider" />
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(){@Overridepublic 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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