狂刷Android范例之3：读写外部存储设备

说明

狂刷Android范例系列文章开张了。每篇学习一个Android范例，将一个范例单独生成一个可运行的app，并对重点源代码进行简要分析。然后提供打包好的源代码下载。
功能

提供一个经典范例，监控Android外部存储设备状态，对公用目录，app私有目录进行读写操作，并展示在app界面上。
代码包在此，无需下载分：
http://download.csdn.net/detail/logicteamleader/8790109
来源

ReadAsset例子来自于Android-20的com.example.android.apis.content.ExternalStorage。
环境

代码运行环境：
1.ADT2014版本；
2.android:minSdkVersion=”8”；android:targetSdkVersion=”20”
3.workspace中已经生成了appcompatv7，它的版本是android-22；
4.需要两个用户权限，读取和写入外部存储。
代码

/* * Copyright (C) 2010 The Android Open Source Project * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */package com.example.externalstorage;//Need the following import to get access to the app resources, since this//class is in a sub-package.import android.app.Activity;import android.content.BroadcastReceiver;import android.content.Context;import android.content.Intent;import android.content.IntentFilter;import android.media.MediaScannerConnection;import android.net.Uri;import android.os.Bundle;import android.os.Environment;import android.util.Log;import android.view.LayoutInflater;import android.view.View;import android.view.ViewGroup;import android.widget.Button;import android.widget.TextView;import java.io.File;import java.io.FileOutputStream;import java.io.IOException;import java.io.InputStream;import java.io.OutputStream;/** * Demonstration of ExternalStorage resources. * 此代码需添加两个权限 * "android.permission.READ_EXTERNAL_STORAGE" * "android.permission.WRITE_EXTERNAL_STORAGE" */public class ExternalStorage extends Activity {    ViewGroup mLayout;    /** * @author wxb * 内部类，两个Button和一个View组成 */    static class Item {        View mRoot;        Button mCreate;        Button mDelete;    }    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",              //得到外部存储图片的公用目录                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);        mExternalStoragePrivatePicture = createStorageControls(                "Picture getExternalFilesDir",              //得到本app外部存储图片的私有目录                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",              //得到本app外部存储文件的私有目录                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();    }    /** * 监测变化，改变按钮可用 */    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);    }    BroadcastReceiver mExternalStorageReceiver;    boolean mExternalStorageAvailable = false;    boolean mExternalStorageWriteable = false;    void updateExternalStorageState() {        //得到外部存储的状态，可读？可写？        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);    }    /** * 监测媒体的mount和remove事件 */    void startWatchingExternalStorage() {        mExternalStorageReceiver = new BroadcastReceiver() {            @Override            public void onReceive(Context context, Intent intent) {                Log.i("test", "Storage: " + intent.getData());                updateExternalStorageState();            }        };        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();    }    /** * 将一个图片拷贝到外部存储的指定文件夹中 */    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() {        // 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 = getExternalFilesDir(Environment.DIRECTORY_PICTURES);        if (path != null) {            File file = new File(path, "DemoPicture.jpg");            file.delete();        }    }    boolean hasExternalStoragePrivatePicture() {        // 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 = getExternalFilesDir(Environment.DIRECTORY_PICTURES);        if (path != null) {            File file = new File(path, "DemoPicture.jpg");            return file.exists();        }        return false;    }     void createExternalStoragePrivateFile() {         // Create a path where we will place our private file on external         // storage.         File file = new File(getExternalFilesDir(null), "DemoFile.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();         } catch (IOException e) {             // Unable to create file, likely because external storage is             // not currently mounted.             Log.w("ExternalStorage", "Error writing " + file, e);         }     }     void deleteExternalStoragePrivateFile() {         // Get path for the file on external storage. If external         // storage is not currently mounted this will fail.         File file = new File(getExternalFilesDir(null), "DemoFile.jpg");         if (file != null) {             file.delete();         }     }     boolean hasExternalStoragePrivateFile() {         // Get path for the file on external storage. If external         // storage is not currently mounted this will fail.         File file = new File(getExternalFilesDir(null), "DemoFile.jpg");         if (file != null) {             return file.exists();         }         return false;     }    /** * 创建一个Item，包含一个view，两个button，以及两个button的点击事件 */    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;    }}
狂刷Android范例之3：读写外部存储设备

狂刷Android范例之3：读写外部存储设备

说明

功能

来源

环境

代码

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