Question

如果列表中没有Photo，如何显示Toast，我正在创建一个应用程序，允许用户拍摄照片并将该照片存储到自动创建的特定文件夹中，

每当我点击“查看”按钮时，如果用户已经拍摄了屏幕，那么它会在列表中显示这些照片，如果用户没有拍摄任何照片然后获取“异常”，那么这里我想要显示一个Toast消息，如果用户有未拍摄任何照片。

logcat的：

07-22 06:48:28.248: E/AndroidRuntime(841): FATAL EXCEPTION: main
07-22 06:48:28.248: E/AndroidRuntime(841): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example/com.example.UploadActivity}: java.lang.NullPointerException
07-22 06:48:28.248: E/AndroidRuntime(841):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
07-22 06:48:28.248: E/AndroidRuntime(841):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
07-22 06:48:28.248: E/AndroidRuntime(841):  at android.app.ActivityThread.access$600(ActivityThread.java:141)
07-22 06:48:28.248: E/AndroidRuntime(841):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
07-22 06:48:28.248: E/AndroidRuntime(841):  at android.os.Handler.dispatchMessage(Handler.java:99)
07-22 06:48:28.248: E/AndroidRuntime(841):  at android.os.Looper.loop(Looper.java:137)
07-22 06:48:28.248: E/AndroidRuntime(841):  at android.app.ActivityThread.main(ActivityThread.java:5041)
07-22 06:48:28.248: E/AndroidRuntime(841):  at java.lang.reflect.Method.invokeNative(Native Method)
07-22 06:48:28.248: E/AndroidRuntime(841):  at java.lang.reflect.Method.invoke(Method.java:511)
07-22 06:48:28.248: E/AndroidRuntime(841):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
07-22 06:48:28.248: E/AndroidRuntime(841):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
07-22 06:48:28.248: E/AndroidRuntime(841):  at dalvik.system.NativeStart.main(Native Method)
07-22 06:48:28.248: E/AndroidRuntime(841): Caused by: java.lang.NullPointerException
07-22 06:48:28.248: E/AndroidRuntime(841):  at com.example.UploadActivity.getSD(UploadActivity.java:125)
07-22 06:48:28.248: E/AndroidRuntime(841):  at com.example.UploadActivity.onCreate(UploadActivity.java:106)
07-22 06:48:28.248: E/AndroidRuntime(841):  at android.app.Activity.performCreate(Activity.java:5104)
07-22 06:48:28.248: E/AndroidRuntime(841):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
07-22 06:48:28.248: E/AndroidRuntime(841):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
07-22 06:48:28.248: E/AndroidRuntime(841):  ... 11 more

SingleAngelActivity.java：

  Button captureButton = (Button) findViewById(R.id.btnCapture);
    Log.d(SingleAngelActivity.LOG_TAG, "captureButton :: " + captureButton);
    captureButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            mCamera.takePicture(null, null, mPicture);
            Log.d(SingleAngelActivity.LOG_TAG, "mCamera.takePicture :: " + mCamera);                                            
        }
    });

    Button viewButton = (Button) findViewById(R.id.btnView);
    Log.d(SingleAngelActivity.LOG_TAG, "SingleAngelActivityButton :: " + viewButton);
    viewButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {  
            Intent intentNewEvent = new Intent(SingleAngelActivity.this, UploadActivity.class);
            startActivity(intentNewEvent);                  
        }
    });

UploadActivity.java：

private List <String> getSD()
        {
            List <String> it = new ArrayList <String>();

            String string = "/mnt/sdcard/Pictures/MyNewImages/";
            File f = new File (string+ SingleAngelActivity.customFolder+ "/");

            Log.d(UploadActivity.LOG_TAG, "KEY_TITLE :::--- " + f);
            File[] files = f.listFiles ();
            Log.d(UploadActivity.LOG_TAG, "getListImages() :::--- " + files);

            for (int i = 0; i <files.length; i++)           
            {
                File  file = files[i];
                Log.d(UploadActivity.LOG_TAG, "i<files.length() :::--- " + i);
                Log.d("Count",file.getPath());
                it.add (file.getPath());
            }
            Log.d(UploadActivity.LOG_TAG, "List <String> it :::--- " + it);
            return it;
        }

Answer 1

仅在安装了SD卡，路径正确且没有其他问题时才有效。它只是检查文件夹是否有任何文件

尝试以下代码

private List <String> getSD()
    {
        List <String> it = new ArrayList <String>();

        String string = "/mnt/sdcard/Pictures/MyNewImages/";
        File f = new File (string+ SingleAngelActivity.customFolder+ "/");

        Log.d(UploadActivity.LOG_TAG, "KEY_TITLE :::--- " + f);
        File[] files = f.listFiles ();
        Log.d(UploadActivity.LOG_TAG, "getListImages() :::--- " + files);
        if(files == null)
         Toast.MakeText(this,"No photo",700).show();
        else
        for (int i = 0; i <files.length; i++)           
        {
            File  file = files[i];
            Log.d(UploadActivity.LOG_TAG, "i<files.length() :::--- " + i);
            Log.d("Count",file.getPath());
            it.add (file.getPath());
        }
        Log.d(UploadActivity.LOG_TAG, "List <String> it :::--- " + it);
        return it;
    }

空指针异常SD卡文件夹没有照片

1 个答案: