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发表于 更新于 分类于

5 Content Provider(3)

在databasetest中新建一个文件DatabaseProvider.java/创建内容提供器

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public class DatabaseProvider extends ContentProvider {

    public static final int BOOK_DIR = 0;
    public static final int BOOK_ITEM = 1;
    public static final int CATEGORY_DIR =2;
    public static final int CATEGORY_ITEM = 3;
    public static final String AUTHORITY = "com.example.databasetest.provider";
    public static UriMatcher uriMatcher;
    private MyDatabaseHelper dbHelper;
    static{
        uriMatcher =  new UriMatcher(UriMatcher.NO_MATCH);
        //注册需要的Uri
        uriMatcher.addURI(AUTHORITY, "book", BOOK_DIR);//参数3是要返回的匹配码
        uriMatcher.addURI(AUTHORITY, "book/#", BOOK_ITEM);
        uriMatcher.addURI(AUTHORITY, "category", CATEGORY_DIR);
        uriMatcher.addURI(AUTHORITY, "category/#", CATEGORY_ITEM);
    }//静态代码块，对UriMatcher初始化
    //将期望匹配的3种URI格式添加进去
    //--常量 UriMatcher.NO_MATCH 表示不匹配任何路径的返回码
    //--# 号为通配符
    //--* 号为任意字符
    @Override
    public boolean onCreate() {
        // TODO: Implement this to initialize your content provider on startup.
        //创建或升级数据库
        dbHelper = new MyDatabaseHelper(getContext(), "BookStore.db", null, 2);
        return true;
    }
//    public DatabaseProvider() {
//    }
    @Override
    public Cursor query(Uri uri, String[] projection, String selection,
                        String[] selectionArgs, String sortOrder) {
        // TODO: Implement this to handle query requests from clients.
        //创建SQLiteDatabase实例
        SQLiteDatabase db = dbHelper.getReadableDatabase();
        Cursor cursor = null;
        switch(uriMatcher.match(uri)){
            case BOOK_DIR:
                cursor  = db.query("Book", projection, selection, selectionArgs, null, null, sortOrder);
                break;
            case BOOK_ITEM:
                //将URI的AUTHORITY之后的部分用 / 符号分割，放到一个列表中
                //不包含元字符串最左端的部分
                String bookId = uri.getPathSegments().get(1);
                cursor = db.query("Book", projection, "id = ?", new String[]{bookId}, null, null, sortOrder);
                break;
            case CATEGORY_DIR:
                cursor = db.query("Category", projection, selection, selectionArgs, null, null, sortOrder);
                break;
            case CATEGORY_ITEM:
                String categoryId = uri.getPathSegments().get(1);
                cursor = db.query("Category", projection, "id = ?", new String[]{ categoryId }, null, null, sortOrder);
                break;
            default:
                break;
        }
        return cursor; //返回cursor
    }
    @Override
    public Uri insert(Uri uri, ContentValues values) {
        // TODO: Implement this to handle requests to insert a new row.
        SQLiteDatabase db = dbHelper.getWritableDatabase();
        Uri uriReturn = null;
        switch(uriMatcher.match(uri)){
            case BOOK_DIR:
            case BOOK_ITEM:
                long newBookId = db.insert("Book", null, values);//返回新增的行号
                uriReturn = Uri.parse("content://"+AUTHORITY+"/book/"+newBookId);
                break;
            case CATEGORY_DIR:
            case CATEGORY_ITEM:
                long newCategoryId = db.insert("Category", null, values);
                uriReturn = Uri.parse("content://"+AUTHORITY+ "/category/"+newCategoryId);
                break;
            default:
                break;
        }
        return uriReturn;
    }
    @Override
    public int update(Uri uri, ContentValues values, String selection,
                      String[] selectionArgs) {
        // TODO: Implement this to handle requests to update one or more rows.
        SQLiteDatabase db = dbHelper.getWritableDatabase();
        int updatedRows =0;
        switch (uriMatcher.match(uri)){
            case BOOK_DIR:
                updatedRows = db.update("Book", values, selection, selectionArgs);
                break;
            case BOOK_ITEM:
                String bookId = uri.getPathSegments().get(1);
                updatedRows = db.update("Book", values, "id = ?", new String[]{bookId});
                break;
            case CATEGORY_DIR:
                updatedRows = db.update("Category", values, selection, selectionArgs);
                break;
            case CATEGORY_ITEM:
                String categoryId = uri.getPathSegments().get(1);
                updatedRows = db.update("Category", values, "id = ?", new String[]{categoryId});
                break;
            default:
                break;
        }
        return updatedRows;
    }

    @Override
    public int delete(Uri uri, String selection, String[] selectionArgs) {
        // Implement this to handle requests to delete one or more rows.
        SQLiteDatabase db = dbHelper.getWritableDatabase();
        int deletedRows =  0;
        switch(uriMatcher.match(uri)){
            case BOOK_DIR:
                deletedRows = db.delete("Book", selection, selectionArgs);
                break;
            case BOOK_ITEM:
                String bookId = uri.getPathSegments().get(1);
                deletedRows = db.delete("Book", "id = ?", new String[]{bookId});
                break;
            case CATEGORY_DIR:
                deletedRows = db.delete("Category", selection, selectionArgs);
                break;
            case CATEGORY_ITEM:
                String categoryId = uri.getPathSegments().get(1);
                deletedRows = db.delete("Category", "id = ?", new String[]{categoryId});
                break;
            default:
                break;
        }
        return deletedRows;
    }
    @Override
    public String getType(Uri uri) { //用于获取Uri对象MIME类型（字符串）
        // TODO: Implement this to handle requests for the MIME type of the data
        // at the given URI.
        switch (uriMatcher.match(uri)){
            case BOOK_DIR:
                return "vnd.android.cursor.dir/vnd.example.databasetest.provider.book";
            case BOOK_ITEM:
                return "vnd.android.cursor.item./vnd.example.databasetest.provider.book";
            case CATEGORY_DIR:
                return "vnd.android.cursor.dir/vnd.example.databasetest.provider.category";
            case CATEGORY_ITEM:
                return "vnd.android.cursor.item/vnd.example.databasetest.provider.category";
        }
        return null;
    }
}
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发表于 更新于 分类于

5 Content Provider(2)

ContentResolver的用法/访问其他应用程序的数据/跨程序共享数据

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public class MainActivity extends AppCompatActivity {

    ArrayAdapter<String> adapter;
    List<String> contactsList = new ArrayList<>();
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        ListView contactsView = (ListView)findViewById(R.id.contacts_list);
        adapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, contactsList); //设置适配器
        contactsView.setAdapter(adapter);
        if (ContextCompat.checkSelfPermission(this, Manifest.permission.READ_CONTACTS) != PackageManager.PERMISSION_GRANTED){
            ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.READ_CONTACTS}, 1);
        }else{
            readContacts();
        }
    }
    private void readContacts() {
        Cursor cursor = null;
        try {
          // CONTENT_URI常量是ContactsContract.CommonDataKinds.Phone类做好的封装
            cursor = getContentResolver().query(ContactsContract.CommonDataKinds.Phone.CONTENT_URI, null, null, null, null);
            if (cursor != null){
                while(cursor.moveToNext()){
                    String displayName = cursor.getString(cursor.getColumnIndex(ContactsContract.CommonDataKinds.Phone.DISPLAY_NAME));
                    String number = cursor.getString(cursor.getColumnIndex(ContactsContract.CommonDataKinds.Phone.NUMBER));
                    contactsList.add(displayName+"\n"+number); // 将数据添加到ListView
                }
                adapter.notifyDataSetChanged(); //通知刷新一下ListView
            }
        }catch (Exception e){
            e.printStackTrace();
        }finally {
            if(cursor != null){
                cursor.close();
            }
        }
    }
    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        switch(requestCode){
            case 1:
                if (grantResults.length>0&&grantResults[0]==PackageManager.PERMISSION_GRANTED){
                    readContacts();
                }else{
                    Toast.makeText(this, "权限获取失败", Toast.LENGTH_SHORT).show();
                }
                break;
            default:
        }
    }
}

发表于 更新于 分类于

5 Content Provider(1)

运行时权限

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private void onClick(View v) {
        if (ContextCompat.checkSelfPermission(MainActivity.this,
                Manifest.permission.CALL_PHONE) != PackageManager.PERMISSION_GRANTED) {//判断是否已经授权
            ActivityCompat.requestPermissions(MainActivity.this,
                    new String[]{Manifest.permission.CALL_PHONE}, 1);//获取权限
        }else{
            call();
        }
    }

    private void call() {//拨打电话的逻辑操作
        try{
            Intent intent = new Intent(Intent.ACTION_CALL);
            intent.setData(Uri.parse("tel:10086")); //Uri.parse()解析成Uri对象
            startActivity(intent);
        } catch (SecurityException e) {
            e.printStackTrace();
        }
    }
<!-- more -->

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        switch (requestCode){ //判断获取权限结果
            case 1:
                if(grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED){
                    call();
                }else  {
                    Toast.makeText(this, "获取权限失败", Toast.LENGTH_SHORT).show();
                }
                break;
            default:
        }
    }

发表于 更新于 分类于

4 Data(4)

LitePal 3.0

添加依赖、配置

  • build.gradle
    implementation 'org.litepal.android:java:3.0.0'

  • AndroidManifest.xml: application添加
    android:name="org.litepal.LitePalApplication"

  • 在app/src/main新建assets/litepal.xml

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    <?xml version="1.0" encoding="utf-8" ?>
    <litepal>
    <!--    数据库名称-->
        <dbname  value="LitePalDemo"/>
    <!--    版本-->
        <version value="1"/>
        <list>
    <!--        注册NewsBean表-->
            <mapping class="com.example.litepaltest.NewsBean"/>
        </list>
    </litepal>
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发表于 更新于 分类于

4 Data(1)

文件存储读取

  • 存储

    • save()
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      private void save(String inputText) throws IOException {
            FileOutputStream out = null;
            BufferedWriter writer = null;
            try {
                out = openFileOutput("data", Context.MODE_PRIVATE);
                writer = new BufferedWriter(new OutputStreamWriter(out));
                writer.write(inputText);
            }catch (IOException e){
                e.printStackTrace();
            }finally{
                try {
                    if(writer != null){
                        writer.close();
                    }
                }catch (IOException e){
                    e.printStackTrace();
                }
            }
        }
    • 在onDestroy()中保存
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      protected void onDestroy() { //将输入内容存入文件中
            super.onDestroy();
            String inputText = edit.getText().toString();
            try {
                save(inputText);
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
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发表于 更新于 分类于

4 Data(2)

SharedPreferences

  • 保存数据(onCreate方法内)
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    Button saveData = findViewById(R.id.save_data);
            saveData.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    SharedPreferences.Editor editor = getSharedPreferences("data", MODE_PRIVATE).edit();
                    editor.putString("name", "Tom");
                    editor.putInt("age", 28);
                    editor.putBoolean("married", false);
                    editor.apply();
                }
            });
  • 读取数据(onCreate方法内)
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    Button restoreData = findViewById(R.id.restore_data);
            restoreData.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    SharedPreferences pref = getSharedPreferences("data", MODE_PRIVATE);
                    String name = pref.getString("name", ""); // 通过键读取值
                    int age = pref.getInt("age", 0);
                    boolean married = pref.getBoolean("married", true);
                    Log.i("---", "name "+name);
                    Log.i("---", "age "+age);
                    Log.i("---", "married "+married);
                }
            });

发表于 更新于 分类于

4 Data(3)

SQLite

创建SQLiteOpenHelper继承类

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public class MyDatabaseHelper extends SQLiteOpenHelper {

    public static final String CREATE_BOOK = "create table Book ("
            +"id integer primary key autoincrement, " //autoincrement: 自增长，自动生成id列的值
            +"author text, "
            +"price real, "
            +"name text)";
    private Context mContext;
    public MyDatabaseHelper(Context context, String name, SQLiteDatabase.CursorFactory factory, int version){
        super(context, name, factory, version);
        mContext = context;
    }
    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL(CREATE_BOOK);
        Toast.makeText(mContext, "create succeeded", Toast.LENGTH_SHORT).show();
    }

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

    }
}
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发表于 更新于 分类于

3 Broadcast

动态注册监听网络变化

  • 例子

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    public class MainActivity extends AppCompatActivity {

        private IntentFilter intentFilter;
        private NetWorkChangeReceiver netWorkChangeReceiver;
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
    //       intentFilter
            intentFilter = new IntentFilter();
            intentFilter.addAction("android.net.conn.CONNECTIVITY_CHANGE");
            netWorkChangeReceiver = new NetWorkChangeReceiver();
    //        registerReceiver
            registerReceiver(netWorkChangeReceiver, intentFilter);
        }

        @Override
        protected void onDestroy() {
            super.onDestroy();
    //        unregisterReceiver
            unregisterReceiver(netWorkChangeReceiver);
        }
    //   广播接收器
        class NetWorkChangeReceiver extends BroadcastReceiver{
            @Override
            public void onReceive(Context context, Intent intent) {
    //          ConnectivityManager
                ConnectivityManager connectivityManager = (ConnectivityManager) getSystemService(context.CONNECTIVITY_SERVICE);
                NetworkInfo networkInfo = connectivityManager.getActiveNetworkInfo();
                if(networkInfo != null && networkInfo.isAvailable()){
                    Toast.makeText(context, "Network Available", Toast.LENGTH_SHORT).show();
                }else{
                    Toast.makeText(context, "Network unavailable", Toast.LENGTH_SHORT).show();
                }
            }
        }
    }
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发表于 更新于 分类于

2 Fragment

一种嵌入到活动中的UI片段

碎片

  • java: news, NewsContentFragment, NewsTitleFragment, activity_main,
    xml: news_content_flag, news_content, news_title_flag, news_item

    关联

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    left_fragment.xml-->LeftFragment.java
    right_fragment.xml-->RightFragment.java
    another_right_fragment.xml-->AnotherRightFragment.java
  • 以LeftFragment为例
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    <?xml version="1.0" encoding="utf-8"?>
    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
        android:orientation="vertical"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <Button
            android:id="@+id/button"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center_horizontal"
            android:text="Button" />
    </LinearLayout>
    <!-- more -->

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    public class LeftFragment extends Fragment {
        @Nullable
        @Override
        public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
            View view = inflater.inflate(R.layout.left_fragment, container, false);
            return view;
        }
    }
    LeftFragment继承自Fragment，将left_fragment加载进来。
  • activity_main.xml
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    <?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:orientation="horizontal"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        tools:context=".MainActivity">

        <fragment
            android:id="@+id/left_fragment"
            android:name="com.example.fragmenttest.LeftFragment"
            android:layout_width="0dp"
            android:layout_weight="1"
            android:layout_height="match_parent"
            />

        <fragment
            android:id="@+id/right_fragment"
            android:name="com.example.fragmenttest.RightFragment"
            android:layout_width="0dp"
            android:layout_height="match_parent"
            android:layout_weight="1" />
    </LinearLayout>
    android:name属性显式指明碎片名。

    动态添加碎片

    创建another_right_fragment和AnotherRightFragment，按下左侧按钮将右侧碎片替换成AnotherRightFragment。
  • replaceFragment()(在MainActivity中)
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    public void replaceFragment(Fragment fragment){
        // 获取FragmentManager
        FragmentManager fragmentManager = getSupportFragmentManager();
        // 开启一个事务
        FragmentTransaction transaction = fragmentManager.beginTransaction();
        // 向容器内添加或替换碎片
        transaction.replace(R.id.right_layout, fragment );
        // 按下Back键返回上个碎片
        transaction.addToBackStack(null);
        // 提交事务
        transaction.commit();
    }

    碎片与活动之间的通信

  • 活动中获取碎片
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    RightFragment rightFragment = (RightFragment) getFragmentManager().findFragmentById(R.id.right_fragment);
  • 碎片中获取活动
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    MainActivity activity = (MainActivity) getActivity();

    动态加载布局技巧

  • 使用限定符
    layout-large/activity_main, layout/activity_main
  • 使用最小宽度限定符
    res/layout-sw600dp/activity_main

    碎片的生命周期

    碎片的回调方法

  • onAttach()
  • onCreateView() 为碎片
  • onActivityCreated()
  • onDestroyView()
  • onDetach()

发表于 更新于 分类于

1 RecyclerView

RecyclerView

  • 调用

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    RecyclerView recyclerView = findViewById(R.id.recycler_view);
    LinearLayoutManager layoutManager = new LinearLayoutManager(this);
    recyclerView.setLayoutManager(layoutManager);
    FruitAdapter adapter = new FruitAdapter(fruitList);
    recyclerView.setAdapter(adapter);
    • 控件
      • id: recycler_view
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        <androidx.recyclerview.widget.RecyclerView
          android:id="@+id/recycler_view"
          android:layout_width="match_parent"
          android:layout_height="match_parent" />
      • id: fruit_name, fruit_image
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