Getting Null pointer exception while saving the im

I want to save an image into sd card.But only the folder naming the image file is created in the sd card,but the actual file is not being created in the sd card.I am getting null pointer exception while trying to save that image to sd card.This is the code:

public class MainActivity extends Activity {
    ImageView bmImage; 
    LinearLayout view1;
      /** Called when the activity is first created. */
      @Override
      public void onCreate(Bundle savedInstanceState) {
          super.onCreate(savedInstanceState);
          setContentView(R.layout.activity_main);

          view1 = (LinearLayout)findViewById(R.id.certlinear);
          bmImage = (ImageView)findViewById(R.id.certimage);

        Button button =(Button)findViewById(R.id.btn);
        button.setOnClickListener(hello);

    }
        Button.OnClickListener hello= new Button.OnClickListener()
        {  
            @Override  
            public void onClick(View v)
            {   
                  View view = view1.getRootView();
                  //u can use any view of your View instead of TextView

                 if(view!=null)
                 {
                 System.out.println("view is not null.....");
                 view.setDrawingCacheEnabled(true);
                 view.buildDrawingCache();
                 Bitmap bm = view.getDrawingCache();

                 try
                 {
                 if(bm!=null)
                 {
                 System.out.println("bm is not null.....");
                 OutputStream fos = null;
                 File folder = new File(Environment.getExternalStorageDirectory().toString() + "/sample.JPEG");
                 boolean success = false;
                 if (!folder.exists()) {
                     success = folder.mkdirs();
                 }
                 if (!success) {
                     // Do something on success
                 } else {
                     // Do something else on failure 
                 }
                 Toast.makeText(MainActivity.this,"path of the folder is "+folder.getAbsolutePath(), Toast.LENGTH_SHORT).show();

                 fos = new FileOutputStream(folder);

                 BufferedOutputStream bos = new BufferedOutputStream(fos);
                 bm.compress(Bitmap.CompressFormat.JPEG, 50, bos);

                 bos.flush();
                 bos.close();
                 view.setDrawingCacheEnabled(false);
                 }
                 }
                 catch(Exception e)
                 {
                 System.out.println("Error="+e);
                 e.printStackTrace();
                 }
                 }

            }
        };
}

This is the exception log:

09-13 18:44:18.957: W/System.err(3612): java.io.FileNotFoundException: /sdcard/sample.JPEG
09-13 18:44:18.967: W/System.err(3612):     at org.apache.harmony.luni.platform.OSFileSystem.open(OSFileSystem.java:244)
09-13 18:44:18.967: W/System.err(3612):     at java.io.FileOutputStream.<init>(FileOutputStream.java:97)
09-13 18:44:18.967: W/System.err(3612):     at java.io.FileOutputStream.<init>(FileOutputStream.java:69)
09-13 18:44:18.976: W/System.err(3612):     at com.example.mytest.MainActivity$1.onClick(MainActivity.java:96)
09-13 18:44:18.976: W/System.err(3612):     at android.view.View.performClick(View.java:2364)
09-13 18:44:18.976: W/System.err(3612):     at android.view.View.onTouchEvent(View.java:4179)
09-13 18:44:18.976: W/System.err(3612):     at android.widget.TextView.onTouchEvent(TextView.java:6541)
09-13 18:44:18.976: W/System.err(3612):     at android.view.View.dispatchTouchEvent(View.java:3709)
09-13 18:44:18.976: W/System.err(3612):     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:884)
09-13 18:44:18.987: W/System.err(3612):     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:884)
09-13 18:44:18.987: W/System.err(3612):     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:884)
09-13 18:44:18.987: W/System.err(3612):     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:884)
09-13 18:44:18.997: W/System.err(3612):     at com.android.internal.policy.impl.PhoneWindow$DecorView.superDispatchTouchEvent(PhoneWindow.java:1659)
09-13 18:44:18.997: W/System.err(3612):     at com.android.internal.policy.impl.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1107)
09-13 18:44:18.997: W/System.err(3612):     at android.app.Activity.dispatchTouchEvent(Activity.java:2061)
09-13 18:44:18.997: W/System.err(3612):     at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:1643)
09-13 18:44:18.997: W/System.err(3612):     at android.view.ViewRoot.handleMessage(ViewRoot.java:1691)
09-13 18:44:18.997: W/System.err(3612):     at android.os.Handler.dispatchMessage(Handler.java:99)
09-13 18:44:18.997: W/System.err(3612):     at android.os.Looper.loop(Looper.java:123)
09-13 18:44:18.997: W/System.err(3612):     at android.app.ActivityThread.main(ActivityThread.java:4363)
09-13 18:44:19.011: W/System.err(3612):     at java.lang.reflect.Method.invokeNative(Native Method)
09-13 18:44:19.011: W/System.err(3612):     at java.lang.reflect.Method.invoke(Method.java:521)
09-13 18:44:19.011: W/System.err(3612):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:860)
09-13 18:44:19.011: W/System.err(3612):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618)
09-13 18:44:19.011: W/System.err(3612):     at dalvik.system.NativeStart.main(Native Method)

I am getting null pointer exception in this line:

   fos = new FileOutputStream(folder);

Thanks in advance.

回答1:

Just simple change needs in your code, try as following,

File folder = new File(Environment.getExternalStorageDirectory().toString());
boolean success = false;
if (!folder.exists()) {
    success = folder.mkdirs();
}

File file = new File(Environment.getExternalStorageDirectory().toString() + "/sample.JPEG");
if (!file.exists()) {
    success = file.createNewFile();
}

回答2:

Have you added this permission

    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>

回答3:

You call

success = folder.mkdirs();

That maks a folder named /sdcard (which exists) and a folder name /sdcard/sample.JPEG The path where you want to write your image is a directory. You can't open an OutputStream on a directory.

回答4:

This works good in my project:

private void saveChicaDress(Bitmap dress){

        String path = Environment.getExternalStorageDirectory().toString() + 
                        getResources().getString(R.string.path_to_store);

        OutputStream fOut = null;
        File file = new File(path, "chica.png");

        int i = 1;  
        while(file.exists()){
            file = new File(path, "chica("+String.valueOf(i)+").png");
            ++i;
        }

        file.getParentFile().mkdirs();

        try {
            fOut = new FileOutputStream(file);
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

        dress.compress(Bitmap.CompressFormat.PNG, 100, fOut);

        try {
            fOut.flush();
            fOut.close();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
}

and in AndroidManifest:

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>