camera.takepicture不工作

Question

I am trying to secretly click photos of someone. I am getting front facing camera, and camera object. But, when I try to click takepicture, my app crashes.

package com.example.xx.xx;

import android.app.Activity;
import android.content.pm.PackageManager;
import android.hardware.Camera;
import android.hardware.Camera.CameraInfo;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Toast;

public class MainActivity extends Activity {
    public final static String DEBUG_TAG = "MakePhotoActivity";
    private Camera camera;
    private int cameraId = 0;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);


    }

    public void onClick(View view) {

        // do we have a camera?
        if (!getPackageManager()
                .hasSystemFeature(PackageManager.FEATURE_CAMERA)) {
            Toast.makeText(this, "No camera on this device", Toast.LENGTH_LONG)
                    .show();
        } else {
            cameraId = findFrontFacingCamera();
            if (cameraId < 0) {
                Toast.makeText(this, "No front facing camera found.",
                        Toast.LENGTH_LONG).show();
            } else {
                getCamera();
                camera.takePicture(null, null,
                        new PhotoHandler(this));
            }
        }
    }

    private void getCamera()
    {
        releaseCameraAndPreview();
        camera = Camera.open(cameraId);
        Log.d(DEBUG_TAG,"found the camera.");
        Log.d(DEBUG_TAG,"Camera is" + camera);

        camera.startPreview();
    }

    private int findFrontFacingCamera() {
        int cameraId = -1;
        // Search for the front facing camera
        int numberOfCameras = Camera.getNumberOfCameras();
        for (int i = 0; i < numberOfCameras; i++) {
            CameraInfo info = new CameraInfo();
            Camera.getCameraInfo(i, info);
            if (info.facing == CameraInfo.CAMERA_FACING_FRONT) {
                Log.d(DEBUG_TAG, "Camera found");
                cameraId = i;
                break;
            }
        }
        Log.d(DEBUG_TAG,"the camera id is" + cameraId);
        return cameraId;
    }
    private void releaseCameraAndPreview() {
        if (camera != null) {
            camera.release();
            camera = null;
        }
    }


    @Override
    protected void onPause() {
        if (camera != null) {
            camera.release();
            camera = null;
        }
        super.onPause();
    }
}

Output I am getting here is:

04-29 06:21:29.994 3608-3608/com.example.khan.hiddencamera D/MakePhotoActivity: Camera found
04-29 06:21:29.994 3608-3608/com.example.khan.hiddencamera D/MakePhotoActivity: the camera id is1
04-29 06:21:30.274 3608-3608/com.example.khan.hiddencamera D/MakePhotoActivity: found the camera.
04-29 06:21:30.274 3608-3608/com.example.khan.hiddencamera D/MakePhotoActivity: Camera isandroid.hardware.Camera@41b2b330
04-29 06:21:30.284 3608-3608/com.example.khan.hiddencamera W/dalvikvm: threadid=1: thread exiting with uncaught exception (group=0x416e9e30)
04-29 06:21:30.314 3608-3608/com.example.khan.hiddencamera E/AndroidRuntime: FATAL EXCEPTION: main

Process: com.example.khan.hiddencamera, PID: 3608
                                                                             java.lang.IllegalStateException: Could not execute method of the activity
                                                                                 at android.view.View$1.onClick(View.java:3855)
                                                                                 at android.view.View.performClick(View.java:4480)
                                                                                 at android.view.View$PerformClick.run(View.java:18609)
                                                                                 at android.os.Handler.handleCallback(Handler.java:733)
                                                                                 at android.os.Handler.dispatchMessage(Handler.java:95)
                                                                                 at android.os.Looper.loop(Looper.java:157)
                                                                                 at android.app.ActivityThread.main(ActivityThread.java:5637)
                                                                                 at java.lang.reflect.Method.invokeNative(Native Method)
                                                                                 at java.lang.reflect.Method.invoke(Method.java:515)
                                                                                 at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:896)
                                                                                 at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:712)
                                                                                 at dalvik.system.NativeStart.main(Native Method)
                                                                              Caused by: java.lang.reflect.InvocationTargetException
                                                                                 at java.lang.reflect.Method.invokeNative(Native Method)
                                                                                 at java.lang.reflect.Method.invoke(Method.java:515)
                                                                                 at android.view.View$1.onClick(View.java:3850)
                                                                                 at android.view.View.performClick(View.java:4480) 
                                                                                 at android.view.View$PerformClick.run(View.java:18609) 
                                                                                 at android.os.Handler.handleCallback(Handler.java:733) 
                                                                                 at android.os.Handler.dispatchMessage(Handler.java:95) 
                                                                                 at android.os.Looper.loop(Looper.java:157) 
                                                                                 at android.app.ActivityThread.main(ActivityThread.java:5637) 
                                                                                 at java.lang.reflect.Method.invokeNative(Native Method) 
                                                                                 at java.lang.reflect.Method.invoke(Method.java:515) 
                                                                                 at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:896) 
                                                                                 at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:712) 
                                                                                 at dalvik.system.NativeStart.main(Native Method) 
                                                                              Caused by: java.lang.RuntimeException: takePicture failed
                                                                                 at android.hardware.Camera.native_takePicture(Native Method)
                                                                                 at android.hardware.Camera.takePicture(Camera.java:1709)
                                                                                 at android.hardware.Camera.takePicture(Camera.java:1626)
                                                                                 at com.example.khan.hiddencamera.MainActivity.onClick(MainActivity.java:43)
                                                                                 at java.lang.reflect.Method.invokeNative(Native Method) 
                                                                                 at java.lang.reflect.Method.invoke(Method.java:515) 
                                                                                 at android.view.View$1.onClick(View.java:3850) 
                                                                                 at android.view.View.performClick(View.java:4480) 
                                                                                 at android.view.View$PerformClick.run(View.java:18609) 
                                                                                 at android.os.Handler.handleCallback(Handler.java:733) 
                                                                                 at android.os.Handler.dispatchMessage(Handler.java:95) 
                                                                                 at android.os.Looper.loop(Looper.java:157) 
                                                                                 at android.app.ActivityThread.main(ActivityThread.java:5637) 
                                                                                 at java.lang.reflect.Method.invokeNative(Native Method) 
                                                                                 at java.lang.reflect.Method.invoke(Method.java:515) 
                                                                                 at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:896) 
                                                                                 at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:712) 
                                                                                 at dalvik.system.NativeStart.main(Native Method) 

Answer 1

Your code seems to be fine. Did you added permission in manifest?

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

Answer 2

You need to define the camera handler callback method

void onPictureTaken(byte[] data, Camera camera)

https://developer.android.com/reference/android/hardware/Camera.PictureCallback.html

Answer 3

5. Important : Pass a fully initialized SurfaceHolder to setPreviewDisplay(SurfaceHolder). Without a surface, the camera will be unable to start the preview.

You can call takePicture() only after the preview display is ready (after your surfaceCreated() ) callback is invoked.