Android组件之ContentProvider（二）——共享单词本

一个共享生词本的应用以熟悉ContentProvider和sqlite基本用法：

应用dictprovider

word数据封装类：

public final class Words{    // 定义该ContentProvider的Authorities    public static final String AUTHORITY            = "com.example.mrpeng.dictprovider";    // 定义一个静态内部类，定义该ContentProvider所包含的数据列的列名    public static final class Word implements BaseColumns    {        // 定义Content所允许操作的三个数据列        public final static String _ID = "_id";        public final static String WORD = "word";        public final static String DETAIL = "detail";        // 定义该Content提供服务的两个Uri        public final static Uri DICT_CONTENT_URI = Uri                .parse("content://" + AUTHORITY + "/words");        public final static Uri WORD_CONTENT_URI = Uri                .parse("content://" + AUTHORITY + "/word");    }}

自定义的provider

public class DictProvider extends ContentProvider {    private static UriMatcher matcher            = new UriMatcher(UriMatcher.NO_MATCH);    private static final int WORDS = 1;    private static final int WORD = 2;    private MyDataBaseHelper dbOpenHelper;    static {        // 为UriMatcher注册两个Uri        matcher.addURI(Words.AUTHORITY, "words", WORDS);        matcher.addURI(Words.AUTHORITY, "word/#", WORD);    }    // 第一次调用该DictProvider时，系统先创建DictProvider对象，并回调该方法    @Override    public boolean onCreate() {        dbOpenHelper = new MyDataBaseHelper(this.getContext(),                "myDict.db3", 1);        return true;    }    // 返回指定Uri参数对应的数据的MIME类型    @Override    public String getType(Uri uri) {        switch (matcher.match(uri)) {            // 如果操作的数据是多项记录            case WORDS:                return "vnd.android.cursor.dir/org.crazyit.dict";            // 如果操作的数据是单项记录            case WORD:                return "vnd.android.cursor.item/org.crazyit.dict";            default:                throw new IllegalArgumentException("未知Uri:" + uri);        }    }    // 查询数据的方法    @Override    public Cursor query(Uri uri, String[] projection, String where,                        String[] whereArgs, String sortOrder) {        SQLiteDatabase db = dbOpenHelper.getReadableDatabase();        switch (matcher.match(uri)) {            // 如果Uri参数代表操作全部数据项            case WORDS:                // 执行查询                return db.query("dict", projection, where,                        whereArgs, null, null, sortOrder);            // 如果Uri参数代表操作指定数据项            case WORD:                // 解析出想查询的记录ID                long id = ContentUris.parseId(uri);                String whereClause = Words.Word._ID + "=" + id;                // 如果原来的where子句存在，拼接where子句                if (where != null && !"".equals(where)) {                    whereClause = whereClause + " and " + where;                    Log.e("mrpeng", "whereClause+=where::: " + whereClause);                }                return db.query("dict", projection, whereClause, whereArgs,                        null, null, sortOrder);            default:                throw new IllegalArgumentException("未知Uri:" + uri);        }    }    // 插入数据方法    @Override    public Uri insert(Uri uri, ContentValues values) {        // 获得数据库实例        SQLiteDatabase db = dbOpenHelper.getReadableDatabase();        switch (matcher.match(uri)) {            // 如果Uri参数代表操作全部数据项            case WORDS:                // 插入数据，返回插入记录的ID                long rowId = db.insert("dict", Words.Word._ID, values);                // 如果插入成功返回uri                if (rowId > 0) {                    // 在已有的 Uri的后面追加ID                    Uri wordUri = ContentUris.withAppendedId(uri, rowId);                    // 通知数据已经改变                    getContext().getContentResolver()                            .notifyChange(wordUri, null);                    return wordUri;                }                break;            default:                throw new IllegalArgumentException("未知Uri:" + uri);        }        return null;    }    // 修改数据的方法    @Override    public int update(Uri uri, ContentValues values, String where,                      String[] whereArgs) {        SQLiteDatabase db = dbOpenHelper.getWritableDatabase();        // 记录所修改的记录数        int num = 0;        switch (matcher.match(uri)) {            // 如果Uri参数代表操作全部数据项            case WORDS:                num = db.update("dict", values, where, whereArgs);                break;            // 如果Uri参数代表操作指定数据项            case WORD:                // 解析出想修改的记录ID                long id = ContentUris.parseId(uri);                String whereClause = Words.Word._ID + "=" + id;                // 如果原来的where子句存在，拼接where子句                if (where != null && !where.equals("")) {                    whereClause = whereClause + " and " + where;                }                num = db.update("dict", values, whereClause, whereArgs);                break;            default:                throw new IllegalArgumentException("未知Uri:" + uri);        }        // 通知数据已经改变        getContext().getContentResolver().notifyChange(uri, null);        return num;    }    // 删除数据的方法    @Override    public int delete(Uri uri, String where, String[] whereArgs) {        SQLiteDatabase db = dbOpenHelper.getReadableDatabase();        // 记录所删除的记录数        int num = 0;        // 对uri进行匹配        switch (matcher.match(uri)) {            // 如果Uri参数代表操作全部数据项            case WORDS:                num = db.delete("dict", where, whereArgs);                break;            // 如果Uri参数代表操作指定数据项            case WORD:                // 解析出所需要删除的记录ID                long id = ContentUris.parseId(uri);                String whereClause = Words.Word._ID + "=" + id;                // 如果原来的where子句存在，拼接where子句                if (where != null && !where.equals("")) {                    whereClause = whereClause + " and " + where;                }                num = db.delete("dict", whereClause, whereArgs);                break;            default:                throw new IllegalArgumentException("未知Uri:" + uri);        }        // 通知数据已经改变        getContext().getContentResolver().notifyChange(uri, null);        return num;    }}

自定义SqliteOpentHelper

public class MyDataBaseHelper extends SQLiteOpenHelper {    final String CREATE_TABLE_SQL =            "create table dict(_id integer primary " +                    "key autoincrement , word , detail)";    public MyDataBaseHelper(Context context, String name, int version) {        super(context, name, null, version);    }    @Override    public void onCreate(SQLiteDatabase db) {        db.execSQL(CREATE_TABLE_SQL);    }    @Override    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {        Log.e("mrpeng", "onUpgrade: " + oldVersion + "---->" + newVersion);    }}

主界面

public class MainActivity extends AppCompatActivity {    private MyDataBaseHelper dbHelper;    private Button insert;    private Button search;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        File dir = Environment.getExternalStorageDirectory();//Gets the Android data directory        String path = dir.getPath();        Log.e("mrpeng", "path: "+path );        dbHelper = new MyDataBaseHelper(this, "myDict.db3", 1);        insert = (Button) findViewById(R.id.insert);        search = (Button) findViewById(R.id.search);        insert.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                String word = ((EditText) findViewById(R.id.word)).getText().toString();                String detail = ((EditText) findViewById(R.id.detail)).getText().toString();                SQLiteDatabase readableDatabase = dbHelper.getReadableDatabase();                // 执行插入语句                readableDatabase.execSQL("insert into dict values(null , ? , ?)"                        , new String[] {word, detail });            }        });        search.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                // 获取用户输入                String key = ((EditText) findViewById(R.id.key)).getText()                        .toString();                // 执行查询                Cursor cursor = dbHelper.getReadableDatabase().rawQuery(                        "select * from dict where word like ? or detail like ?",                        new String[] { "%" + key + "%", "%" + key + "%" });                ArrayList<Map<String, String>> list = converCursorToList(cursor);                Bundle bundle = new Bundle();                bundle.putSerializable("data",list);                Intent intent = new Intent(MainActivity.this, ResultActivity.class);                intent.putExtras(bundle);                startActivity(intent);            }        });    }    private ArrayList<Map<String,String>> converCursorToList(Cursor cursor) {        ArrayList<Map<String, String>> list= new ArrayList<>();        while (cursor.moveToNext()){            HashMap<String, String> map = new HashMap<>();            map.put("word",cursor.getString(1));            map.put("detail",cursor.getString(2));            list.add(map);        }        return list;    }}

结果展示页

public class ResultActivity extends Activity {    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.popup);        ListView listView = (ListView) findViewById(R.id.show);        Intent intent = getIntent();        Bundle data = intent.getExtras();        List<Map<String,String>> list = (List<Map<String, String>>) data.getSerializable("data");        // 将List封装成SimpleAdapter        SimpleAdapter adapter = new SimpleAdapter(ResultActivity.this                , list,                R.layout.line, new String[] { "word", "detail" }                , new int[] {R.id.word, R.id.detail });        listView.setAdapter(adapter);    }}

manifests

<?xml version="1.0" encoding="utf-8"?><manifest xmlns:android="http://schemas.android.com/apk/res/android"    package="com.example.mrpeng.dictprovider">    <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>        <activity            android:name=".ResultActivity"            android:theme="@android:style/Theme.Material.Dialog" />        <provider            android:authorities="com.example.mrpeng.dictprovider"            android:name=".DictProvider"            android:exported="true"/>    </application></manifest>

dictResolver应用

数据封装类 Word 结果展示类ResultActivity同应用dictprovider

主界面

public class MainActivity extends AppCompatActivity {    private ContentResolver contentResolver;    private Button insert;    private Button search;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        contentResolver = getContentResolver();        insert = (Button) findViewById(R.id.insert);        search = (Button) findViewById(R.id.search);        insert.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                // 获取用户输入                String word = ((EditText) findViewById(R.id.word))                        .getText().toString();                String detail = ((EditText) findViewById(R.id.detail))                        .getText().toString();                //插入生词记录                ContentValues values = new ContentValues();                values.put(Words.Word.WORD,word);                values.put(Words.Word.DETAIL,detail);                contentResolver.insert(Words.Word.DICT_CONTENT_URI,values);                Toast.makeText(MainActivity.this,"添加生词成功",Toast.LENGTH_SHORT).show();            }        });        // 为search按钮的单击事件绑定事件监听器        search.setOnClickListener(new View.OnClickListener()        {            @Override            public void onClick(View source)            {                // 获取用户输入                String key = ((EditText) findViewById(R.id.key))                        .getText().toString();                // 执行查询                Cursor cursor = contentResolver.query(                        Words.Word.DICT_CONTENT_URI, null,                        "word like ? or detail like ?", new String[] {                                "%" + key + "%", "%" + key + "%" }, null);                // 创建一个Bundle对象                Bundle data = new Bundle();                data.putSerializable("data", converCursorToList(cursor));                // 创建一个Intent                Intent intent = new Intent(MainActivity.this,                        ResultActivity.class);                intent.putExtras(data);                // 启动Activity                startActivity(intent);            }        });    }    private ArrayList<Map<String, String>> converCursorToList(Cursor cursor)    {        ArrayList<Map<String, String>> result = new ArrayList<>();        // 遍历Cursor结果集        while (cursor.moveToNext())        {            // 将结果集中的数据存入ArrayList中            Map<String, String> map = new HashMap<>();            // 取出查询记录中第2列、第3列的值            map.put(Words.Word.WORD, cursor.getString(1));            map.put(Words.Word.DETAIL, cursor.getString(2));            result.add(map);        }        return result;    }}

由以上代码可以看出，ContentProvider负责直接对数据库操作，并对外暴露接口，如果别的应用可以通过ContentProvider对外暴露的api对数据库进行间接的操作