Android应用使用ContentProvider共享数据

1.

在当前应用新建一个MyContentProvider：Flie–>new–>other–>Content Provider，Class Name写MyContentProvider，URI Authority随便填个，我填的是com.jerehedu.ch08.mycontentprovider，点击确定即可。

2.

MyContentProvider.java里面代码如下：

package com.example.ygd.jreduch08;

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

import com.example.ygd.jreduch08.dbhelper.MyDbHelper;

public class MyContentProvider extends ContentProvider {
private MyDbHelper openHelper;
private static final UriMatcher MATCHER=new UriMatcher(UriMatcher.NO_MATCH);    //声明一个urimatcher
static{//注册两个URL
MATCHER.addURI("com.jerehedu.ch08.mycontentprovider","info",1);   //访问info表所有信息    主机名在清单文件中有，路径填数据库名
MATCHER.addURI("com.jerehedu.ch08.mycontentprovider","info/#",2);//根据id来访问
}

@Override
public String getType(Uri uri) {
switch (MATCHER.match(uri)){
case 1:
return "vnd.android.cursor.dir/info";
case 2:
return "vnd.android.cursor.item/info";
}
return null;
}

public MyContentProvider() {
}

@Override
public int delete(Uri uri, String selection, String[] selectionArgs) {
SQLiteDatabase db=openHelper.getWritableDatabase();
switch (MATCHER.match(uri)){
case 1:
return db.delete("info",selection,selectionArgs);
case 2:
long rowid=ContentUris.parseId(uri);   //从uri中拿到id
String where="_id="+rowid;
if(selection!=null&&!selection.equals("")){
where=selection+" and "+where;
return db.delete("info",where,selectionArgs);
}
}
return 0;
}

@Override
public Uri insert(Uri uri, ContentValues values) {
SQLiteDatabase db=openHelper.getWritableDatabase();
switch (MATCHER.match(uri)){
case 1:
long rowid=db.insert("info",null,values);
return ContentUris.withAppendedId(uri,rowid);
default:
break;
}
return null;
}

@Override
public boolean onCreate() {
openHelper=new MyDbHelper(this.getContext(),1);
return false;
}

@Override
public Cursor query(Uri uri, String[] projection, String selection,
String[] selectionArgs, String sortOrder) {
SQLiteDatabase db=openHelper.getReadableDatabase();
switch (MATCHER.match(uri)){
case 1:
return db.query("info",projection,selection,selectionArgs,null,null,sortOrder);
case 2:
long rowid=ContentUris.parseId(uri);
String where="_id="+rowid;
if(selection!=null&&!selection.equals("")){
where=selection+" and "+where;
}
return db.query("info",projection,where,selectionArgs,null,null,sortOrder);
}
return null;
}

@Override
public int update(Uri uri, ContentValues values, String selection,
String[] selectionArgs) {
SQLiteDatabase db=openHelper.getWritableDatabase();
switch (MATCHER.match(uri)){
case 1:
return db.update("info",values,selection,selectionArgs);
case 2:
long rowid=ContentUris.parseId(uri);
String where="_id="+rowid;
if(selection!=null&&!selection.equals("")){
where=selection+" and "+where;
}
return db.update("info",values,where,selectionArgs);
}
return 0;
}
}

3

新建一个项目，就叫MyContentProviderTest，添加两个Button：查询和添加；再添加一个TextView，用来展示数据，主函数如下:

package com.example.ygd.mycontentprovidertest;

import android.content.ContentResolver;
import android.content.ContentValues;
import android.database.Cursor;
import android.net.Uri;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {
private Button bt1,bt2;
private TextView show;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
bt1= (Button) findViewById(R.id.getUser);
bt2= (Button) findViewById(R.id.insert);
show= (TextView) findViewById(R.id.show);
bt1.setOnClickListener(new View.OnClickListener() {     //bt1用来查询数据
@Override
public void onClick(View v) {
Uri uri=Uri.parse("content://com.jerehedu.ch08.mycontentprovider/info");
ContentResolver resolver=getContentResolver();
Cursor cs=resolver.query(uri,null,null,null,null);
StringBuffer sbff=new StringBuffer();
while(cs.moveToNext()){
sbff.append(cs.getString(0));
sbff.append(cs.getString(1));
sbff.append(cs.getString(2));
sbff.append(cs.getString(3));
sbff.append(cs.getString(4));
}
show.setText(sbff.toString());
}
});

bt2.setOnClickListener(new View.OnClickListener() {     //bt2用来插入数据
@Override
public void onClick(View v) {
addUser();
Toast.makeText(MainActivity.this, "插入成功", Toast.LENGTH_SHORT).show();
}
});
}

public void addUser(){
Uri uri=Uri.parse("content://com.jerehedu.ch08.mycontentprovider/info");
ContentResolver resolver=getContentResolver();
ContentValues values=new ContentValues();
values.put("name","外星人");
values.put("pwd","123");
values.put("age","0");
values.put("imgUrl","http://adfjak.com");
resolver.insert(uri,values);
}
}

这样就实现了不同应用的数据共享。