Android 内容提供者 一个查询内容小demo

Android 内容提供者

以下是demo的代码：

首先 先将下面的项目放到Android Studio里：

http://pan.baidu.com/s/1kUMYMGn

是个压缩包 （其实压缩包里已经创建好了）

在项目的java路径下面新建一个新得文件夹 com.dzz.provider

在里面在新建一个MyProvider 文件

MyProvider 文件代码：

package com.dzz.provider;

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 android.support.annotation.Nullable;
import android.util.Log;

import com.dzz.db.DbHelper;

/**
* Created by 朝花偏不夕拾 on 2017/2/14.
*/

public class MyProvider extends ContentProvider {

private SQLiteDatabase sqLiteDatabase;
private UriMatcher uriMatcher;

private static final int PERSONS=1;
private static final int PERSON=2;

@Override
public boolean onCreate() {
Log.i("test","onCreate");

DbHelper dbHelper=new DbHelper(getContext(),"question.db",null,2);
sqLiteDatabase = dbHelper.getReadableDatabase();

//实例化URL匹配器
uriMatcher = new UriMatcher(UriMatcher.NO_MATCH);
//添加匹配规则
//http://localhost:8080/xxx/000.action
//规则 ：
//        content://com.dzz.android24_sqlite.person/persons   //查询单个
//        content://com.dzz.android24_sqlite.person/persons/#   //条件查询
uriMatcher.addURI("com.dzz.android24_sqlite.person","persons",MyProvider.PERSONS);
uriMatcher.addURI("com.dzz.android24_sqlite.person","persons/#",MyProvider.PERSON);

return false;
}

@Nullable
@Override   //Cursor  是个结果
public Cursor query(Uri uri, String[] strings, String s, String[] strings1, String s1) {
Log.i("test","query");

int code= uriMatcher.match(uri);
switch (code) {
case MyProvider.PERSONS:
Log.i("test","query所有");
//查询所有的数据
return sqLiteDatabase.query(true,"person",strings,s,strings1,null,null,s1,null);
case MyProvider.PERSON:
Log.i("test","query单个");
//获取#的值
long cc= ContentUris.parseId(uri);
return sqLiteDatabase.rawQuery("select * from person where _id=?",new String[]{cc+""});
}
return null;

}

@Nullable
@Override
public String getType(Uri uri) {
Log.i("test","getType");
return null;
}

@Nullable
@Override
public Uri insert(Uri uri, ContentValues contentValues) {
Log.i("test","insert");
return null;
}

@Override
public int delete(Uri uri, String s, String[] strings) {
Log.i("test","delete");
return 0;
}

@Override
public int update(Uri uri, ContentValues contentValues, String s, String[] strings) {
Log.i("test","update");
return 0;
}
}

还要在这个项目的清单文件配置 提供者

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.dzz.android24_sqlite">

<application
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:supportsRtl="true"
android:theme="@style/AppTheme">
<activity android:name=".MainActivity">
<intent-filter>
<action android:name="android.intent.action.MAIN" />

<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>

<!--配置提供者内容-->
<provider
android:authorities="com.dzz.android24_sqlite.person"
android:name="com.dzz.provider.MyProvider"
android:exported="true"
></provider>

</application>

</manifest>

然后在新建一个项目 因为我们要取到上一个项目里的值

先写下XML

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools" android:id="@+id/activity_main"
android:layout_width="match_parent" android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
android:orientation="vertical"
tools:context="com.dzz.android24_contentresolver.MainActivity">

<EditText
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="@+id/et_main"
/>
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="获取数据"
android:onClick="getData"
/>
</LinearLayout>

最后给获取数据加上点击 可以查看你取到值了没有

package com.dzz.android24_contentresolver;

import android.content.ContentResolver;
import android.database.Cursor;
import android.net.Uri;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.text.TextUtils;
import android.util.Log;
import android.view.View;
import android.widget.EditText;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {

private ContentResolver cr;
private EditText et_main;
private Uri uri;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
et_main = (EditText) findViewById(R.id.et_main);

//获取内容访问者
cr =getContentResolver();
}

public void getData(View view){
if(TextUtils.isEmpty(et_main.getText())){
//查询所有
//              //前面必须要加content://
uri = Uri.parse("content://com.dzz.android24_sqlite.person/persons");
}else{
//查询单个
String ss=et_main.getText().toString();
uri = Uri.parse("content://com.dzz.android24_sqlite.person/persons/"+ss);

}

Cursor cursor= cr.query(uri,null,null,null,null);

//查询单个
//        1.   条件  id=1;
//        2.   网页：
//        3.   URL 匹配器

while(cursor.moveToNext()){
int id=cursor.getInt(cursor.getColumnIndex("_id"));
String name=cursor.getString(cursor.getColumnIndex("name"));
int age=cursor.getInt(cursor.getColumnIndex("age"));
Log.i("test",id+"___"+name+"+++"+age);
Toast.makeText(this, id+"___"+name+"+++"+age, Toast.LENGTH_SHORT).show();
}

}

}