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【Android基础】ContentProvider简例

2020年07月09日 | 移动技术网IT编程 | 我要评论

布局文件

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity"
    android:orientation="vertical">

    <EditText
        android:id="@+id/id"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="id,just for delete or update"/>

    <EditText
        android:id="@+id/url"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="url,for add or update"/>

    <Button
        android:id="@+id/add"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Add"/>

    <Button
        android:id="@+id/delete"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Delete"/>

    <Button
        android:id="@+id/query"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Query"/>

    <Button
        android:id="@+id/update"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="update"/>

    <TextView
        android:id="@+id/result"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"/>

</LinearLayout>

清单文件

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

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <provider
            android:name=".UrlContentProvider"
            android:authorities="com.example.mycontentprovider"
            android:enabled="true"
            android:exported="true"></provider>

        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

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

</manifest>

DatabaseHelper 类

package com.example.contentprovidertest;

import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;

import androidx.annotation.Nullable;

public class UrlDatabaseHelper extends SQLiteOpenHelper {
    //数据库文件名
    static final String DATABASE_NAME = "url.db";
    //数据库表名
    static final String TABLE_NAME = "url";
    //数据库版本号
    private static final int DATABASE_VERSION = 1;

    public UrlDatabaseHelper(@Nullable Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }

    //创建表
    //表中含有_id和url
    private void createTable(SQLiteDatabase db) {
        db.execSQL("CREATE TABLE " + TABLE_NAME + "(_id INTEGER PRIMARY KEY AUTOINCREMENT," + "url TEXT)");
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        createTable(db);
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

    }
}

ContentProvider 类

package com.example.contentprovidertest;

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

public class UrlContentProvider extends ContentProvider {

    //与AndroidManifest.xml文件中authorities相同
    protected static final String AUTHORITY = "com.example.mycontentprovider";
    //创建UriMatcher对象
    private static UriMatcher uriMatcher;
    //匹配成功后的匹配码
    private static final int MATCH_CODE = 100;

    //Content uri of this provider
    //组成："content://" + AUTHORITY + “/” + addURI中第二个参数
    public static final Uri uri = Uri.parse("content://com.example.mycontentprovider/");

    private UrlDatabaseHelper mOpenHelper;

    //创建静态代码块
    static {
        //实例化UriMatcher对象
        uriMatcher = new UriMatcher(UriMatcher.NO_MATCH);
        //可以实现匹配URI的功能
        //参数1：authority 参数2：路径 参数3：URI与给定组件匹配成功后的匹配码
        uriMatcher.addURI(AUTHORITY, null, MATCH_CODE);
    }

    @Override
    public boolean onCreate() {
        // Implement this to initialize your content provider on startup.
        //创建DatabaseHelper对象
        mOpenHelper = new UrlDatabaseHelper(getContext());
        return true;
    }

    @Override
    public int delete(Uri uri, String selection, String[] selectionArgs) {
        //得到SQLiteDatabase对象
        SQLiteDatabase db = mOpenHelper.getWritableDatabase();
        int rows = -1;
        switch (uriMatcher.match(uri)){
            case MATCH_CODE:
                rows = db.delete(UrlDatabaseHelper.TABLE_NAME,selection,selectionArgs);
                break;
        }
        return rows;
    }

    @Override
    public Uri insert(Uri uri, ContentValues values) {
        //得到SQLiteDatabase对象
        SQLiteDatabase db = mOpenHelper.getWritableDatabase();
        switch (uriMatcher.match(uri)){
            case MATCH_CODE:
                db.insert(UrlDatabaseHelper.TABLE_NAME,null,values);
                break;
        }
        return uri;
    }

    @Override
    public Cursor query(Uri uri, String[] projection, String selection,
                        String[] selectionArgs, String sortOrder) {
        //得到SQLiteDatabase对象
        SQLiteDatabase db = mOpenHelper.getWritableDatabase();
        Cursor cursor = null;
        switch (uriMatcher.match(uri)){
            case MATCH_CODE:
                cursor = db.query(UrlDatabaseHelper.TABLE_NAME,projection,selection,selectionArgs,null,null,sortOrder);
                break;
        }
        return cursor;
    }

    @Override
    public int update(Uri uri, ContentValues values, String selection,
                      String[] selectionArgs) {
        //得到SQLiteDatabase对象
        SQLiteDatabase db = mOpenHelper.getWritableDatabase();
        int rows = -1;
        switch (uriMatcher.match(uri)){
            case MATCH_CODE:
                rows = db.update(UrlDatabaseHelper.TABLE_NAME,values,selection,selectionArgs);
                break;
        }
        return rows;
    }

    @Override
    public String getType(Uri uri) {
        // Implement this to handle requests for the MIME type of the data
        // at the given URI.
        throw new UnsupportedOperationException("Not yet implemented");
    }
}

增删查改操作

package com.example.contentprovidertest;

import androidx.appcompat.app.AppCompatActivity;

import android.content.ContentResolver;
import android.content.ContentValues;
import android.database.Cursor;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity implements View.OnClickListener {
    private EditText mIDEditText;
    private EditText mUrlEditText;
    private Button mButtonAdd;
    private Button mButtonDelete;
    private Button mButtonQuery;
    private Button mButtonupdate;
    private TextView mResult;

    private ContentResolver mContentResolver;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        //初始化控件
        init();

        mContentResolver = getContentResolver();

        mButtonAdd.setOnClickListener(this);
        mButtonDelete.setOnClickListener(this);
        mButtonQuery.setOnClickListener(this);
        mButtonupdate.setOnClickListener(this);
    }

    private void init() {
        mIDEditText = findViewById(R.id.id);
        mUrlEditText = findViewById(R.id.url);
        mButtonAdd = findViewById(R.id.add);
        mButtonDelete = findViewById(R.id.delete);
        mButtonQuery = findViewById(R.id.query);
        mButtonupdate = findViewById(R.id.update);
        mResult = findViewById(R.id.result);
    }

    @Override
    public void onClick(View v) {
        switch (v.getId()){
            case R.id.add:
                String url = mUrlEditText.getText().toString();
                ContentValues contentValues = new ContentValues();
                contentValues.put("url",url);
                mContentResolver.insert(UrlContentProvider.uri,contentValues);
                break;
            case R.id.delete:
                String id = mIDEditText.getText().toString();
                String whereClause = "_id" + "=?";
                String[] whereArgs = new String[]{id};
                mContentResolver.delete(UrlContentProvider.uri,whereClause,whereArgs);
                break;
            case R.id.update:
                String urlUpdate = mUrlEditText.getText().toString();
                ContentValues CV = new ContentValues();
                CV.put("url",urlUpdate);
                String idUpdate = mIDEditText.getText().toString();
                String whereClauseUpdate = "_id" + "=?";
                String[] whereArgsUpdate = new String[]{idUpdate};
                mContentResolver.update(UrlContentProvider.uri,CV,whereClauseUpdate,whereArgsUpdate);
                break;
            case R.id.query:
                StringBuffer stringBuffer = new StringBuffer();
                Cursor cursor = mContentResolver.query(UrlContentProvider.uri,null,null,null,null);
                cursor.moveToFirst();
                do {
                    String urlQuery = cursor.getString(cursor.getColumnIndex("url"));
                    stringBuffer.append(urlQuery);
                    stringBuffer.append("///");
                } while(cursor.moveToNext());
                mResult.setText(stringBuffer);
                break;
        }
    }
}

本文地址：https://blog.csdn.net/m0_46211029/article/details/107176771

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验证码：

【Android基础】ContentProvider简例

2020年07月09日 | 移动技术网IT编程 | 我要评论

布局文件

清单文件

DatabaseHelper 类

ContentProvider 类

增删查改操作

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