Android中的外部存储答案

【问题标题】：External Storage in AndroidAndroid中的外部存储
【发布时间】：2012-03-30 08:42:13
【问题描述】：

我正在尝试将 ArrayList 保存到 Android 应用程序的外部存储中，但似乎每次都失败，但我不知道为什么。我已按照有关使用外部存储的在线教程进行操作，但我看不出与我拥有的代码有什么不同。这是我的阅读功能：

public static ArrayList<MapRoute> readFile(Context context, String filename) {

        ObjectInputStream ois = null;
        ArrayList<MapRoute> result = null;

        if (!externalStorageAvailable || !externalStorageWritable) {
            Log.d("READ FAILED", Environment.getExternalStorageState());
            return null;
        }

        try {
            File file = new File(context.getExternalFilesDir(null), filename);
            FileInputStream fis = new FileInputStream(file);
            ois = new ObjectInputStream(fis);
            result = (ArrayList<MapRoute>)ois.readObject();
            ois.close();
        } catch (Exception e) {
            Log.d("FAILED", "READ FAILED");
        } finally {
            try {
                if (ois != null) {
                    ois.close();
                }
            } catch (IOException e) {
                Log.d("ENDREAD", "FAIL");
            }
        }

        return result;
    }

然后写：

public static boolean saveFile(Context context, ArrayList<MapRoute> routes, String filename) {

        if (!externalStorageAvailable && !externalStorageWritable) {
            Log.d("FAILED", "FAIL");
            return false;
        }

        File file = new File(context.getExternalFilesDir(null), filename);
        ObjectOutputStream oos = null;
        boolean success = false;

        try {
            OutputStream os = new FileOutputStream(file);
            oos = new ObjectOutputStream(os);
            oos.writeObject(routes);
            success = true;
        } catch (IOException e) {
            Log.d("OOS", "FAILED");
        } finally {
            try {
                if (oos != null) {
                    oos.close();
                }
            } catch (IOException e) {
                Log.d("OOS", "FAILED2");
            }
        }

        return success;
    }

在我的 logcat 消息中，来自 readFile 函数内的 try 块的消息 FAILED READ FAILED 被输出，我不确定这是否与我尝试读取数组列表的方式有关。

对此的任何帮助将不胜感激。

编辑：这是堆栈跟踪

    03-13 22:20:33.690: W/System.err(25353): java.io.WriteAbortedException: Read an      exception; java.io.NotSerializableException: mark.es3.mapRoute.MapRoute
03-13 22:20:33.690: W/System.err(25353):    at java.io.ObjectInputStream.readNonPrimitiveContent(ObjectInputStream.java:933)
03-13 22:20:33.690: W/System.err(25353):    at java.io.ObjectInputStream.readObject(ObjectInputStream.java:2262)
03-13 22:20:33.690: W/System.err(25353):    at java.io.ObjectInputStream.readObject(ObjectInputStream.java:2217)
03-13 22:20:33.690: W/System.err(25353):    at java.util.ArrayList.readObject(ArrayList.java:665)
03-13 22:20:33.690: W/System.err(25353):    at java.lang.reflect.Method.invokeNative(Native Method)
03-13 22:20:33.690: W/System.err(25353):    at java.lang.reflect.Method.invoke(Method.java:507)
03-13 22:20:33.690: W/System.err(25353):    at java.io.ObjectInputStream.readObjectForClass(ObjectInputStream.java:1520)
03-13 22:20:33.690: W/System.err(25353):    at java.io.ObjectInputStream.readHierarchy(ObjectInputStream.java:1443)
03-13 22:20:33.695: W/System.err(25353):    at java.io.ObjectInputStream.readNewObject(ObjectInputStream.java:2112)
03-13 22:20:33.695: W/System.err(25353):    at java.io.ObjectInputStream.readNonPrimitiveContent(ObjectInputStream.java:916)
03-13 22:20:33.695: W/System.err(25353):    at java.io.ObjectInputStream.readObject(ObjectInputStream.java:2262)
03-13 22:20:33.695: W/System.err(25353):    at java.io.ObjectInputStream.readObject(ObjectInputStream.java:2217)
03-13 22:20:33.695: W/System.err(25353):    at mark.es3.activities.CreateSessionActivity$FavouriteRoutesTab.readFile(CreateSessionActivity.java:245)
03-13 22:20:33.695: W/System.err(25353):    at mark.es3.activities.CreateSessionActivity$FavouriteRoutesTab.onCreate(CreateSessionActivity.java:148)
03-13 22:20:33.695: W/System.err(25353):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
03-13 22:20:33.695: W/System.err(25353):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1615)
03-13 22:20:33.695: W/System.err(25353):    at android.app.ActivityThread.startActivityNow(ActivityThread.java:1491)
03-13 22:20:33.695: W/System.err(25353):    at android.app.LocalActivityManager.moveToState(LocalActivityManager.java:127)
03-13 22:20:33.700: W/System.err(25353):    at android.app.LocalActivityManager.startActivity(LocalActivityManager.java:339)
03-13 22:20:33.700: W/System.err(25353):    at android.widget.TabHost$IntentContentStrategy.getContentView(TabHost.java:691)
03-13 22:20:33.700: W/System.err(25353):    at android.widget.TabHost.setCurrentTab(TabHost.java:341)
03-13 22:20:33.700: W/System.err(25353):    at android.widget.TabHost$2.onTabSelectionChanged(TabHost.java:140)
03-13 22:20:33.700: W/System.err(25353):    at android.widget.TabWidget$TabClickListener.onClick(TabWidget.java:456)
03-13 22:20:33.700: W/System.err(25353):    at android.view.View.performClick(View.java:2538)
03-13 22:20:33.700: W/System.err(25353):    at android.view.View$PerformClick.run(View.java:9152)
03-13 22:20:33.700: W/System.err(25353):    at android.os.Handler.handleCallback(Handler.java:587)
03-13 22:20:33.700: W/System.err(25353):    at android.os.Handler.dispatchMessage(Handler.java:92)
03-13 22:20:33.700: W/System.err(25353):    at android.os.Looper.loop(Looper.java:123)
03-13 22:20:33.720: W/System.err(25353):    at android.app.ActivityThread.main(ActivityThread.java:3691)
03-13 22:20:33.720: W/System.err(25353):    at java.lang.reflect.Method.invokeNative(Native Method)
03-13 22:20:33.720: W/System.err(25353):    at java.lang.reflect.Method.invoke(Method.java:507)
03-13 22:20:33.720: W/System.err(25353):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:847)
03-13 22:20:33.720: W/System.err(25353):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:605)
03-13 22:20:33.720: W/System.err(25353):    at dalvik.system.NativeStart.main(Native Method)
03-13 22:20:33.720: W/System.err(25353): Caused by: java.io.NotSerializableException: mark.es3.mapRoute.MapRoute
03-13 22:20:33.720: W/System.err(25353):    at java.io.ObjectOutputStream.writeNewObject(ObjectOutputStream.java:1535)
03-13 22:20:33.720: W/System.err(25353):    at java.io.ObjectOutputStream.writeObjectInternal(ObjectOutputStream.java:1847)
03-13 22:20:33.720: W/System.err(25353):    at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:1689)
03-13 22:20:33.725: W/System.err(25353):    at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:1653)
03-13 22:20:33.725: W/System.err(25353):    at java.util.ArrayList.writeObject(ArrayList.java:651)
03-13 22:20:33.725: W/System.err(25353):    at java.lang.reflect.Method.invokeNative(Native Method)
03-13 22:20:33.725: W/System.err(25353):    at java.lang.reflect.Method.invoke(Method.java:507)
03-13 22:20:33.725: W/System.err(25353):    at java.io.ObjectOutputStream.writeHierarchy(ObjectOutputStream.java:1219)
03-13 22:20:33.725: W/System.err(25353):    at java.io.ObjectOutputStream.writeNewObject(ObjectOutputStream.java:1575)
03-13 22:20:33.725: W/System.err(25353):    at java.io.ObjectOutputStream.writeObjectInternal(ObjectOutputStream.java:1847)
03-13 22:20:33.725: W/System.err(25353):    at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:1689)
03-13 22:20:33.725: W/System.err(25353):    at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:1653)
03-13 22:20:33.725: W/System.err(25353):    at mark.es3.activities.CreateSessionActivity$FavouriteRoutesTab.saveFile(CreateSessionActivity.java:224)
03-13 22:20:33.725: W/System.err(25353):    at mark.es3.activities.CreateSessionActivity$FavouriteRoutesTab.saveRoute(CreateSessionActivity.java:207)
03-13 22:20:33.730: W/System.err(25353):    at mark.es3.activities.PlotRouteActivity.onHandleActionBarItemClick(PlotRouteActivity.java:94)
03-13 22:20:33.730: W/System.err(25353):    at greendroid.app.GDMapActivity$1.onActionBarItemClicked(GDMapActivity.java:247)
03-13 22:20:33.730: W/System.err(25353):    at greendroid.widget.ActionBar$1.onClick(ActionBar.java:396)
03-13 22:20:33.730: W/System.err(25353):    ... 11 more

我的 MapRoute 类确实实现了 Serializable，所以我不确定这意味着什么。

【问题讨论】：

所有设置在清单中？
您的文件是否正在创建？
是的，我的在清单中
@Tim 正在创建文件，我可以使用我的 android 设备上的文件目录浏览到它
在具有“FAILED, READ FAILED”的 catch 块内添加 e.printStackTrace();并在抛出异常时发布出现在您的日志猫中的堆栈跟踪。

标签： android io storage external logcat

【解决方案1】：

您的MapRoute 对象似乎不可序列化，因此您无法将其写入ObjectOutputStream。可能的解决方案：

使MapRoute 和其中使用的所有类都实现Serializable
“手动”进行序列化/反序列化。

【讨论】：