自定义ContentProvider

最新推荐文章于 2022-11-28 00:16:19 发布

时光Fly

最新推荐文章于 2022-11-28 00:16:19 发布

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分类专栏：极客学院笔记

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本文详细介绍了如何利用ContentProvider在Android应用中实现数据的存储和读取操作，包括创建数据库、定义操作接口以及通过ContentResolver进行数据交互。通过示例代码演示了如何向数据库插入数据、查询数据并展示结果。

1.继承ContentProvider

package com.fsg.thinkpad.application;

import android.content.ContentProvider;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.net.Uri;

/**
 * Created by ThinkPad on 2016/2/28.
 */
public class MyProvider extends ContentProvider {
    public static final Uri URI=Uri.parse("content://com.fsg.thinkpad.application");
    SQLiteDatabase sqLiteDatabase;
    @Override
    public boolean onCreate() {
        sqLiteDatabase=getContext().openOrCreateDatabase("mycp.db", Context.MODE_PRIVATE,null);
        sqLiteDatabase.execSQL("create table if not exists tab(" +
                "_id integer primary key autoincrement," +
                "name text);");
        return true;
    }

    @Override
    public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) {
        Cursor cursor=sqLiteDatabase.query("tab",null,null,null,null,null,null);
        return cursor;
    }

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

    @Override
    public Uri insert(Uri uri, ContentValues values) {
        sqLiteDatabase.insert("tab",null,values);
        return null;
    }

    @Override
    public int delete(Uri uri, String selection, String[] selectionArgs) {
        return 0;
    }

    @Override
    public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) {
        return 0;
    }
}

2.主界面

package com.fsg.thinkpad.application;

import android.content.ContentValues;
import android.database.Cursor;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;

public class MainActivity extends AppCompatActivity {

    private static final String TAG = "MainActivity";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }

    public void onClickWriteDB(View view){
        ContentValues values=new ContentValues();
        values.put("name","java");
        getContentResolver().insert(MyProvider.URI, values);
        values.put("name", "c");
        getContentResolver().insert(MyProvider.URI, values);
        values.put("name", "c++");
        getContentResolver().insert(MyProvider.URI, values);
        values.put("name","python");

        getContentResolver().insert(MyProvider.URI,values);
    }

    public void onClickReadDB(View view){
        Cursor cursor=getContentResolver().query(MyProvider.URI, null, null, null, null);
        while (cursor.moveToNext()){
            Log.i(TAG,cursor.getString(cursor.getColumnIndex("name")));
        }
        cursor.close();
    }
}

3.布局文件

<RelativeLayout 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:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:paddingBottom="@dimen/activity_vertical_margin" tools:context=".MainActivity">

    <TextView android:text="@string/hello_world" android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/textView" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="写入数据库"
        android:onClick="onClickWriteDB"
        android:id="@+id/button"
        android:layout_below="@+id/textView"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="88dp" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="查询数据库"
        android:onClick="onClickReadDB"
        android:id="@+id/button2"
        android:layout_below="@+id/button"
        android:layout_alignLeft="@+id/button"
        android:layout_alignStart="@+id/button"
        android:layout_marginTop="125dp" />

</RelativeLayout>