Java 显示摄像头API android拍摄的图像

我一直在遵循本教程：尝试并启用在我的应用程序中拍照。然而，一旦我按下“拍照”按钮，就会出现错误

日志：

    09-16 11:04:00.539  19561-19561/au.gov.nsw.shellharbour.saferroadsshellharbour D/Dob_in_a_Hoon_photos﹕ Failed to create Dob_in_a_Hoon_photos directory
09-16 11:04:00.539  19561-19561/au.gov.nsw.shellharbour.saferroadsshellharbour D/AndroidRuntime﹕ Shutting down VM
09-16 11:04:00.539  19561-19561/au.gov.nsw.shellharbour.saferroadsshellharbour W/dalvikvm﹕ threadid=1: thread exiting with uncaught exception (group=0x40e21438)
09-16 11:04:00.559  19561-19561/au.gov.nsw.shellharbour.saferroadsshellharbour E/AndroidRuntime﹕ FATAL EXCEPTION: main
    java.lang.NullPointerException: file
            at android.net.Uri.fromFile(Uri.java:441)
            at au.gov.nsw.shellharbour.saferroadsshellharbour.dob_in_a_hoon.getOutputMediaFileUri(dob_in_a_hoon.java:97)
            at au.gov.nsw.shellharbour.saferroadsshellharbour.dob_in_a_hoon.captureImage(dob_in_a_hoon.java:89)
            at au.gov.nsw.shellharbour.saferroadsshellharbour.dob_in_a_hoon.access$000(dob_in_a_hoon.java:28)
            at au.gov.nsw.shellharbour.saferroadsshellharbour.dob_in_a_hoon$1.onClick(dob_in_a_hoon.java:60)
            at android.view.View.performClick(View.java:4191)
            at android.view.View$PerformClick.run(View.java:17229)
            at android.os.Handler.handleCallback(Handler.java:615)
            at android.os.Handler.dispatchMessage(Handler.java:92)
            at android.os.Looper.loop(Looper.java:137)
            at android.app.ActivityThread.main(ActivityThread.java:4963)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:511)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1038)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:805)
            at dalvik.system.NativeStart.main(Native Method)
09-16 11:04:10.529  19561-19561/au.gov.nsw.shellharbour.saferroadsshellharbour I/Process﹕ Sending signal. PID: 19561 SIG: 9

这是我的.java文件：

public class dob_in_a_hoon extends ActionBarActivity {

    private static final int CAMERA_CAPTURE_IMAGE_REQUEST_CODE = 100;
    public static final int MEDIA_TYPE_IMAGE = 1;

    private static final String IMAGE_DIRECTORY_NAME = "Dob_in_a_Hoon_photos";

    private Uri fileUri;

    private ImageView Hoon_Image;
    private Button button_take_photo;


    private String driver_spinner_array[];

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_dob_in_a_hoon);
        driver_spinner_array = new String[2];
        driver_spinner_array[0] = "Yes";
        driver_spinner_array[1] = "No";
        Spinner Driver_spinner = (Spinner) findViewById(R.id.driver_selector);
        ArrayAdapter adapter = new ArrayAdapter(this, android.R.layout.simple_dropdown_item_1line, driver_spinner_array);
                Driver_spinner.setAdapter(adapter);

        Hoon_Image = (ImageView) findViewById(R.id.CapturedImage);
        button_take_photo = (Button)findViewById(R.id.btn_take_photo);

        button_take_photo.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                captureImage();
            }
        });

    }


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.dob_in_a_hoon, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();
        if (id == R.id.action_settings) {
            return true;
        }
        return super.onOptionsItemSelected(item);
    }

    private void captureImage(){
        Intent intent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);

        fileUri = getOutputMediaFileUri(MEDIA_TYPE_IMAGE);

        intent.putExtra(MediaStore.EXTRA_OUTPUT, fileUri);

        startActivityForResult(intent, CAMERA_CAPTURE_IMAGE_REQUEST_CODE);
    }

    public Uri getOutputMediaFileUri(int type){
        return Uri.fromFile(getOutputMediaFile(type));
    }

    private static File getOutputMediaFile(int type){
        File mediaStorageDir = new File(Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES),IMAGE_DIRECTORY_NAME);

        if (!mediaStorageDir.exists()){
            if (!mediaStorageDir.mkdirs()){
                Log.d(IMAGE_DIRECTORY_NAME, "Failed to create " + IMAGE_DIRECTORY_NAME + " directory");
                return null;
            }
        }

        String timeStamp = new SimpleDateFormat("yyyyMMdd_HHmmss", Locale.getDefault()).format(new Date());
        File mediaFile;
        if (type==MEDIA_TYPE_IMAGE){
            mediaFile = new File(mediaStorageDir.getPath()+File.separator+"IMG_"+timeStamp+".jpg");
        }else {
            return null;
        }

        return mediaFile;
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data){
        if (requestCode == CAMERA_CAPTURE_IMAGE_REQUEST_CODE){
            if (resultCode==RESULT_OK){
                previewCapturedImage();
            }else if (resultCode == RESULT_CANCELED){
                Toast.makeText(getApplicationContext(),"User Cancelled image Capture", Toast.LENGTH_SHORT).show();
            }else {
                Toast.makeText(getApplicationContext(),"Failed to capture image", Toast.LENGTH_SHORT).show();
            }
        }
    }

    private void previewCapturedImage(){
        try{
            Hoon_Image.setVisibility(View.VISIBLE);
            BitmapFactory.Options options = new BitmapFactory.Options();
            options.inSampleSize = 8;
            final Bitmap bitmap = BitmapFactory.decodeFile(fileUri.getPath(),options);

            Hoon_Image.setImageBitmap(bitmap);
        }catch (NullPointerException e){
            e.printStackTrace();
        }
    }

    @Override
    protected void onSaveInstanceState(Bundle outState){
        super .onSaveInstanceState(outState);

        outState.putParcelable("file_uri", fileUri);
    }

    @Override
    protected void onRestoreInstanceState(Bundle savedInstanceState){
        super.onRestoreInstanceState(savedInstanceState);

        fileUri = savedInstanceState.getParcelable("file_uri");
    }
}

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有人能看到我的代码哪里出了问题，以及我必须做些什么来修复它吗？

我创建了一个示例代码段并测试了mkdir，如代码所示，如果我删除了权限，它会导致类似的异常

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

请检查您的舱单，以确保您已定义这些

---

如果不是上述问题，另一个（不太可能）错误源可能是SD卡空间不足或某些权限限制。在这种情况下，我会在android emulator或其他设备上尝试该应用程序。

这应该添加到清单中以使用摄像头功能：

<uses-feature android:name="android.hardware.camera" />
<uses-feature android:glEsVersion="0x00020000"
              android:required="true"/>

您能否详细说明如何修复它？根据跟踪，getOutputMediaFile可能返回null。你可以在这个函数中添加更多的Log.d消息，或者更好地使用android调试工具。它甚至还没有到达那一行代码——它被抛出到创建目录行中。你在使用emulator吗？我在手机上测试了create dir代码片段，它似乎工作正常没有例外。不，我正在使用物理设备。我甚至没有想过添加权限！德普。非常感谢。