ApiDemos学习知识点Content-ExternalStorage(8)

演示了如何读写外部存储卡。演示了三种情况： 
* 1.向存储卡的共享目录中的图片目录中写入一张图片： 
* 位置为：/storage/sdcard/Pictures 
* 2.向本地应用的图片目录中写入一张图片 
* 位置为：/storage/sdcard/Android/data/包名/files/Pictures 
* 3.向本地应用的目录中写入一个文件 

* 位置为：/storage/sdcard/android/data/包名/files/ 

首先来看下布局和代码吧

<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="match_parent"    android:layout_height="wrap_content"    android:scrollbars="none" >    <LinearLayout        android:id="@+id/layout"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:orientation="vertical" >    </LinearLayout></ScrollView>

item布局

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="match_parent"    android:layout_height="wrap_content"    android:orientation="vertical" >    <TextView        android:id="@+id/label"        style="?android:attr/textAppearanceMediumInverse"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:layout_weight="0"        android:background="#888"        android:padding="4dip"        android:singleLine="true"        android:color="?android:attr/textColorPrimaryInverse" />    <TextView        android:id="@+id/path"        style="?android:attr/textAppearanceSmall"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:layout_weight="0"        android:padding="4dip"        android:singleLine="true" />    <LinearLayout        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:orientation="horizontal" >        <View            android:layout_width="0dip"            android:layout_height="0dip"            android:layout_weight="1" />        <Button            android:id="@+id/create"            android:layout_width="wrap_content"            android:layout_height="wrap_content"            android:layout_weight="1"            android:text="@string/create" />        <View            android:layout_width="0dip"            android:layout_height="0dip"            android:layout_weight="1" />        <Button            android:id="@+id/delete"            android:layout_width="wrap_content"            android:layout_height="wrap_content"            android:layout_weight="1"            android:text="@string/delete" />        <View            android:layout_width="0dip"            android:layout_height="0dip"            android:layout_weight="1" />    </LinearLayout></LinearLayout>

实现功能代码

public class ExternalStorage extends Activity {    ViewGroup mLayout;   //定义一个类，用于管理每种情况的布局，因为是一样的布局，所以可以达到利用的目的    static class Item {        View mRoot;        Button mCreate;        Button mDelete;    }// 定义三种情况下的布局    Item mExternalStoragePublicPicture;    Item mExternalStoragePrivatePicture;    Item mExternalStoragePrivateFile;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.external_storage);        mLayout = (ViewGroup)findViewById(R.id.layout);        mExternalStoragePublicPicture = createStorageControls(                "Picture: getExternalStoragePublicDirectory",                Environment.getExternalStoragePublicDirectory(                        Environment.DIRECTORY_PICTURES),                new View.OnClickListener() {                    public void onClick(View v) {                        createExternalStoragePublicPicture();                        updateExternalStorageState();                    }                },                new View.OnClickListener() {                    public void onClick(View v) {                        deleteExternalStoragePublicPicture();                        updateExternalStorageState();                    }                });        mLayout.addView(mExternalStoragePublicPicture.mRoot);

       // 注意这个方法不在Environment里面而是在Activity当中        mExternalStoragePrivatePicture = createStorageControls(                "Picture getExternalFilesDir",                getExternalFilesDir(Environment.DIRECTORY_PICTURES),                new View.OnClickListener() {                    public void onClick(View v) {                        createExternalStoragePrivatePicture();                        updateExternalStorageState();                    }                },                new View.OnClickListener() {                    public void onClick(View v) {                        deleteExternalStoragePrivatePicture();                        updateExternalStorageState();                    }                });        mLayout.addView(mExternalStoragePrivatePicture.mRoot);        mExternalStoragePrivateFile = createStorageControls(                "File getExternalFilesDir",                getExternalFilesDir(null),                new View.OnClickListener() {                    public void onClick(View v) {                        createExternalStoragePrivateFile();                        updateExternalStorageState();                    }                },                new View.OnClickListener() {                    public void onClick(View v) {                        deleteExternalStoragePrivateFile();                        updateExternalStorageState();                    }                });        mLayout.addView(mExternalStoragePrivateFile.mRoot);        startWatchingExternalStorage();    }    @Override    protected void onDestroy() {        super.onDestroy();        stopWatchingExternalStorage();    }    void handleExternalStorageState(boolean available, boolean writeable) {        boolean has = hasExternalStoragePublicPicture();        mExternalStoragePublicPicture.mCreate.setEnabled(writeable && !has);        mExternalStoragePublicPicture.mDelete.setEnabled(writeable && has);        has = hasExternalStoragePrivatePicture();        mExternalStoragePrivatePicture.mCreate.setEnabled(writeable && !has);        mExternalStoragePrivatePicture.mDelete.setEnabled(writeable && has);        has = hasExternalStoragePrivateFile();        mExternalStoragePrivateFile.mCreate.setEnabled(writeable && !has);        mExternalStoragePrivateFile.mDelete.setEnabled(writeable && has);    }//定义一个广播接收者，用于监视外部存储卡的挂载状态    BroadcastReceiver mExternalStorageReceiver;    boolean mExternalStorageAvailable = false;    boolean mExternalStorageWriteable = false;    void updateExternalStorageState() {        String state = Environment.getExternalStorageState();        if (Environment.MEDIA_MOUNTED.equals(state)) {            mExternalStorageAvailable = mExternalStorageWriteable = true;        } else if (Environment.MEDIA_MOUNTED_READ_ONLY.equals(state)) {            mExternalStorageAvailable = true;            mExternalStorageWriteable = false;        } else {            mExternalStorageAvailable = mExternalStorageWriteable = false;        }        handleExternalStorageState(mExternalStorageAvailable,                mExternalStorageWriteable);    }    void startWatchingExternalStorage() {        mExternalStorageReceiver = new BroadcastReceiver() {            @Override            public void onReceive(Context context, Intent intent) {                Log.i("test", "Storage: " + intent.getData());                updateExternalStorageState();            }        };

    //注册广播接收者        IntentFilter filter = new IntentFilter();        filter.addAction(Intent.ACTION_MEDIA_MOUNTED);        filter.addAction(Intent.ACTION_MEDIA_REMOVED);        registerReceiver(mExternalStorageReceiver, filter);        updateExternalStorageState();    }    void stopWatchingExternalStorage() {        unregisterReceiver(mExternalStorageReceiver);    }    void createExternalStoragePublicPicture() {        // Create a path where we will place our picture in the user's        // public pictures directory.  Note that you should be careful about        // what you place here, since the user often manages these files.  For        // pictures and other media owned by the application, consider        // Context.getExternalMediaDir().        File path = Environment.getExternalStoragePublicDirectory(                Environment.DIRECTORY_PICTURES);        File file = new File(path, "DemoPicture.jpg");        try {            // Make sure the Pictures directory exists.            path.mkdirs();            // Very simple code to copy a picture from the application's            // resource into the external file.  Note that this code does            // no error checking, and assumes the picture is small (does not            // try to copy it in chunks).  Note that if external storage is            // not currently mounted this will silently fail.            InputStream is = getResources().openRawResource(R.drawable.balloons);            OutputStream os = new FileOutputStream(file);            byte[] data = new byte[is.available()];            is.read(data);            os.write(data);            is.close();            os.close();            // Tell the media scanner about the new file so that it is            // immediately available to the user.            MediaScannerConnection.scanFile(this,                    new String[] { file.toString() }, null,                    new MediaScannerConnection.OnScanCompletedListener() {                public void onScanCompleted(String path, Uri uri) {                    Log.i("ExternalStorage", "Scanned " + path + ":");                    Log.i("ExternalStorage", "-> uri=" + uri);                }            });        } catch (IOException e) {            // Unable to create file, likely because external storage is            // not currently mounted.            Log.w("ExternalStorage", "Error writing " + file, e);        }    }    void deleteExternalStoragePublicPicture() {        // Create a path where we will place our picture in the user's        // public pictures directory and delete the file.  If external        // storage is not currently mounted this will fail.        File path = Environment.getExternalStoragePublicDirectory(                Environment.DIRECTORY_PICTURES);        File file = new File(path, "DemoPicture.jpg");        file.delete();    }    boolean hasExternalStoragePublicPicture() {        // Create a path where we will place our picture in the user's        // public pictures directory and check if the file exists.  If        // external storage is not currently mounted this will think the        // picture doesn't exist.        File path = Environment.getExternalStoragePublicDirectory(                Environment.DIRECTORY_PICTURES);        File file = new File(path, "DemoPicture.jpg");        return file.exists();    }    void createExternalStoragePrivatePicture() {        // Create a path where we will place our picture in our own private        // pictures directory.  Note that we don't really need to place a        // picture in DIRECTORY_PICTURES, since the media scanner will see        // all media in these directories; this may be useful with other        // media types such as DIRECTORY_MUSIC however to help it classify        // your media for display to the user.        File path = getExternalFilesDir(Environment.DIRECTORY_PICTURES);        File file = new File(path, "DemoPicture.jpg");        try {            // Very simple code to copy a picture from the application's            // resource into the external file.  Note that this code does            // no error checking, and assumes the picture is small (does not            // try to copy it in chunks).  Note that if external storage is            // not currently mounted this will silently fail.            InputStream is = getResources().openRawResource(R.drawable.balloons);            OutputStream os = new FileOutputStream(file);            byte[] data = new byte[is.available()];            is.read(data);            os.write(data);            is.close();            os.close();            // Tell the media scanner about the new file so that it is            // immediately available to the user.            MediaScannerConnection.scanFile(this,                    new String[] { file.toString() }, null,                    new MediaScannerConnection.OnScanCompletedListener() {                public void onScanCompleted(String path, Uri uri) {                    Log.i("ExternalStorage", "Scanned " + path + ":");                    Log.i("ExternalStorage", "-> uri=" + uri);                }            });        } catch (IOException e) {            // Unable to create file, likely because external storage is            // not currently mounted.            Log.w("ExternalStorage", "Error writing " + file, e);        }    }    void deleteExternalStoragePrivatePicture() {        //         File path = getExternalFilesDir(Environment.DIRECTORY_PICTURES);        if (path != null) {            File file = new File(path, "DemoPicture.jpg");            file.delete();        }    }    boolean hasExternalStoragePrivatePicture() {        // 该方法将一张图片复制到外部存储卡本地应用目录下的图片目录下        File path = getExternalFilesDir(Environment.DIRECTORY_PICTURES);        if (path != null) {            File file = new File(path, "DemoPicture.jpg");            return file.exists();        }        return false;    }// 该方法将一张图片复制到外部存储卡本地应用目录下     void createExternalStoragePrivateFile() {         //          File file = new File(getExternalFilesDir(null), "DemoFile.jpg");         try {             //              InputStream is = getResources().openRawResource(R.drawable.balloons);             OutputStream os = new FileOutputStream(file);             byte[] data = new byte[is.available()];             is.read(data);             os.write(data);             is.close();             os.close();         } catch (IOException e) {                Log.w("ExternalStorage", "Error writing " + file, e);         }     }     void deleteExternalStoragePrivateFile() {         // 删除已存在的文件         File file = new File(getExternalFilesDir(null), "DemoFile.jpg");         if (file != null) {             file.delete();         }     }     boolean hasExternalStoragePrivateFile() {         // 判断是否已经存在该名字的文件         File file = new File(getExternalFilesDir(null), "DemoFile.jpg");         if (file != null) {             return file.exists();         }         return false;     }/*     * 创建每种情况下的布局     */    Item createStorageControls(CharSequence label, File path,            View.OnClickListener createClick,            View.OnClickListener deleteClick) {        LayoutInflater inflater = (LayoutInflater)getSystemService(LAYOUT_INFLATER_SERVICE);        Item item = new Item();        item.mRoot = inflater.inflate(R.layout.external_storage_item, null);        TextView tv = (TextView)item.mRoot.findViewById(R.id.label);        tv.setText(label);        if (path != null) {            tv = (TextView)item.mRoot.findViewById(R.id.path);            tv.setText(path.toString());        }        item.mCreate = (Button)item.mRoot.findViewById(R.id.create);        item.mCreate.setOnClickListener(createClick);        item.mDelete = (Button)item.mRoot.findViewById(R.id.delete);        item.mDelete.setOnClickListener(deleteClick);        return item;    }}