java - 相机错误

Question

这是我在 AndroidManifest.xml 中的权限

<uses-permission android:name="android.permission.CAMERA" />
    <uses-feature android:name="android.hardware.camera" />

这是我的 MainActivity.java:

import android.hardware.Camera;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.FrameLayout;

public class MainActivity extends AppCompatActivity {

    private Camera mCamera;
    private CameraPreview mPreview;

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

        // Create an instance of Camera
        mCamera = getCameraInstance();

        // Create our Preview view and set it as the content of our activity.
        mPreview = new CameraPreview(this, mCamera);
        FrameLayout preview = (FrameLayout) findViewById(R.id.camera_preview);
        preview.addView(mPreview);
    }

    public static Camera getCameraInstance(){
        Camera c = null;
        try {
            c = Camera.open(); // attempt to get a Camera instance
        }
        catch (Exception e){
            // Camera is not available (in use or does not exist)
        }
        return c; // returns null if camera is unavailable
    }
}

这是我的activity_main.xml

<LinearLayout 
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="horizontal"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    >
    <FrameLayout
        android:id="@+id/camera_preview"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:layout_weight="1"
        />

    <Button
        android:id="@+id/button_capture"
        android:text="Capture"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        />
</LinearLayout>

这就是我的 CameraPreview.java:

import android.content.Context;
import android.hardware.Camera;
import android.util.Log;
import android.view.SurfaceHolder;
import android.view.SurfaceView;

import java.io.IOException;

/** A basic Camera preview class */
public class CameraPreview extends SurfaceView implements SurfaceHolder.Callback {
    private SurfaceHolder mHolder;
    private Camera mCamera;

    public CameraPreview(Context context, Camera camera) {
        super(context);
        mCamera = camera;

        // Install a SurfaceHolder.Callback so we get notified when the
        // underlying surface is created and destroyed.
        mHolder = getHolder();
        mHolder.addCallback(this);
        // deprecated setting, but required on Android versions prior to 3.0
        mHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
    }

    public void surfaceCreated(SurfaceHolder holder) {
        // The Surface has been created, now tell the camera where to draw the preview.
        try {
            mCamera.setPreviewDisplay(holder);
            mCamera.startPreview();
        } catch (IOException e) {
            Log.d("Error:", "Error setting camera preview: " + e.getMessage());
        }
    }

    public void surfaceDestroyed(SurfaceHolder holder) {
        // empty. Take care of releasing the Camera preview in your activity.
    }

    public void surfaceChanged(SurfaceHolder holder, int format, int w, int h) {
        // If your preview can change or rotate, take care of those events here.
        // Make sure to stop the preview before resizing or reformatting it.

        if (mHolder.getSurface() == null){
            // preview surface does not exist
            return;
        }

        // stop preview before making changes
        try {
            mCamera.stopPreview();
        } catch (Exception e){
            // ignore: tried to stop a non-existent preview
        }

        // set preview size and make any resize, rotate or
        // reformatting changes here

        // start preview with new settings
        try {
            mCamera.setPreviewDisplay(mHolder);
            mCamera.startPreview();

        } catch (Exception e){
            Log.d("Error:", "Error starting camera preview: " + e.getMessage());
        }
    }
}

当我打开应用程序时，它崩溃并出现此错误:

05-16 16:17:55.694 14553-14553/? E/AndroidRuntime: FATAL EXCEPTION: main
                                                   Process: com.test.badubadu.test, PID: 14553
                                                   java.lang.NullPointerException: Attempt to invoke virtual method 'void android.hardware.Camera.setPreviewDisplay(android.view.SurfaceHolder)' on a null object reference
                                                       at com.test.badubadu.test.CameraPreview.surfaceCreated(CameraPreview.java:31)
                                                       at android.view.SurfaceView.updateWindow(SurfaceView.java:622)
                                                       at android.view.SurfaceView$3.onPreDraw(SurfaceView.java:161)
                                                       at android.view.ViewTreeObserver.dispatchOnPreDraw(ViewTreeObserver.java:944)
                                                       at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:2205)
                                                       at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1250)
                                                       at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:6311)
                                                       at android.view.Choreographer$CallbackRecord.run(Choreographer.java:871)
                                                       at android.view.Choreographer.doCallbacks(Choreographer.java:683)
                                                       at android.view.Choreographer.doFrame(Choreographer.java:619)
                                                       at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:857)
                                                       at android.os.Handler.handleCallback(Handler.java:751)
                                                       at android.os.Handler.dispatchMessage(Handler.java:95)
                                                       at android.os.Looper.loop(Looper.java:241)
                                                       at android.app.ActivityThread.main(ActivityThread.java:6217)
                                                       at java.lang.reflect.Method.invoke(Native Method)
                                                       at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:865)
                                                       at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:755)

编辑错误:

05-16 22:52:39.451 18993-18993/com.test.blaba.test W/CameraBase: An error occurred while connecting to camera 0: Service not available
05-16 22:52:39.451 18993-18993/com.test.blabla.test D/Error:: Error starting camera preview: Fail to connect to camera service
05-16 22:52:39.578 18993-19091/com.test.blaba.test I/Adreno: QUALCOMM build                   : b6da14b, I47548ba842
                                                                Build Date                       : 11/14/16
                                                                OpenGL ES Shader Compiler Version: XE031.09.00.03
                                                                Local Branch                     : 
                                                                Remote Branch                    : quic/LA.BF64.1.2.3_rb1.6
                                                                Remote Branch                    : NONE
                                                                Reconstruct Branch               : NOTHING

所以我不知道错误在哪里......感谢您的帮助...:)

Answer 1

mCamera 为 null，因为 getCameraInstance() 返回 null。最有可能的是，这是因为 Camera.open() 引发了异常。 始终确保您可以看到异常。在早期软件开发期间，这主要是通过记录这些异常(例如，Log.e())。