【Android基础】ContentProvider简例
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2022-04-19 10:33:25
布局文件
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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