Question

我有我的主要活动，其中有几个按钮其中一个应该打开相机为了使它更清晰我使用View.onClick()，所以我将在主Activity上使用Button，其余的将由另一个其他类（Camactivity）管理。

在我的主要活动中：

  Button btnrep = (Button)findViewById(R.id.button3);
  btnrep.setOnClickListener(new Camactivity(this));

和我的

public class Camactivity extends Activity implements View.OnClickListener

    private File imageFile;
    private Context appContext;

    public MainActivity_1(Context context)
    {
        appContext = context;
    }


    @Override
    public void onClick(View view) {

                Intent intent = new Intent(android.provider.MediaStore.ACTION_IMAGE_CAPTURE);//use intent and pass in mediastore
                //mediastore is a databases where image and video are stores and link

                imageFile = new File(Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES), "BreedingGround.bmp");
        /*link to a directory - pass in directory where you want to save the pictures and names of the file*/


                Uri tempuri = Uri.fromFile(imageFile);//Convert imageFile to a Uri
                intent.putExtra(android.provider.MediaStore.EXTRA_OUTPUT, tempuri);//location where u want the image file to be save after taking photo
                intent.putExtra(android.provider.MediaStore.EXTRA_VIDEO_QUALITY, 1);//quality of out image, 1 means high quality image


                startActivityForResult(intent, 0);//Request code 0 to identify who send the request

    }

但是我在startActivityForResult(intent, 0);

收到空指针错误

 FATAL EXCEPTION: main Process: com.example.mohit.softeng, PID: 22075
  java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.pm.PackageManager android.content.Context.getPackageManager()' on a null object reference
      at android.content.ContextWrapper.getPackageManager(ContextWrapper.java:97)
      at com.example.mohit.softeng.MainActivity_1.onClick(MainActivity_1.java:60)
      at android.view.View.performClick(View.java:5697)
      at android.widget.TextView.performClick(TextView.java:10826)
      at android.view.View$PerformClick.run(View.java:22526)
      at android.os.Handler.handleCallback(Handler.java:739)
      at android.os.Handler.dispatchMessage(Handler.java:95)
      at android.os.Looper.loop(Looper.java:158)
      at android.app.ActivityThread.main(ActivityThread.java:7225)
      at java.lang.reflect.Method.invoke(Native Method)
      at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1230)
      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1120)

Answer 1

非常欢迎您定义View.OnClickListener子类，但是我根本没有理由看到Camactivity，所以只需在View.OnClickListener上实施MainActivity即可。

此外，您可能希望startActivityForResult MainActivity中onActivityResult的结果，而不是Camactivity。

所以，有了这个建议

Button btnrep = (Button)findViewById(R.id.button3);
btnrep.setOnClickListener(this);

如果您的Activity已经实现了OnClickListener，那么添加一个if语句来检查单击了哪个按钮。

@Override
public void onClick(View view) {
    switch (v.getId()) {
        case R.id.button3:
            openCamera();
    }
}

private void openCamera() {
    // That other code in Camactivity
}

替代答案......仍未使用new制作活动类。

Button btnrep = (Button)findViewById(R.id.button3);
btnrep.setOnClickListener(new View.onClickListener() {
    @Override
    public void onClick(View v) {
        Intent cam = new Intent(MainActivity.this, Camactivity.class);
        startActivityForResult(cam, 0); // If you need the result in MainAcivity, pass it back from camActivity
        // else, just startActivity(cam);
    }
});

然后，更新Camactivity以在创建相机意图后立即启动它。

public class Camactivity extends Activity {

    private File imageFile;

    @Override
    public void onCreate(Bundle icicle) {
        super.onCreate(icicle);

        Intent intent = new Intent(android.provider.MediaStore.ACTION_IMAGE_CAPTURE);//use intent and pass in mediastore
        //mediastore is a databases where image and video are stores and link

        imageFile = new File(Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES), "BreedingGround.bmp");
/*link to a directory - pass in directory where you want to save the pictures and names of the file*/

        Uri tempuri = Uri.fromFile(imageFile);//Convert imageFile to a Uri
        intent.putExtra(android.provider.MediaStore.EXTRA_OUTPUT, tempuri);//location where u want the image file to be save after taking photo
        intent.putExtra(android.provider.MediaStore.EXTRA_VIDEO_QUALITY, 1);//quality of out image, 1 means high quality image

        startActivityForResult(intent, 0);//Request code 0 to identify who send the request

    } 

    @Override
    public void onActivityResult (int requestCode, int resultCode, Intent data) {
        if (requestCode == 0) {
            // TODO: Handle camera intent result
        }
    }



}

从另一个活动

1 个答案: