android - 在 CameraPreview 上使用 ViewPager

Question

我一直在尝试创建一个 Camera Preview，它在预览上显示一个带有多个透明图像的 View Pager。但是，我收到此错误:

05-10 03:31:23.614: E/AndroidRuntime(674): FATAL EXCEPTION: main
05-10 03:31:23.614: E/AndroidRuntime(674): java.lang.NullPointerException
05-10 03:31:23.614: E/AndroidRuntime(674):  at com.android.gs1.MainActivity$CameraPreview.surfaceCreated(MainActivity.java:102)
05-10 03:31:23.614: E/AndroidRuntime(674):  at android.view.SurfaceView.updateWindow(SurfaceView.java:562)
05-10 03:31:23.614: E/AndroidRuntime(674):  at android.view.SurfaceView.access$000(SurfaceView.java:82)
05-10 03:31:23.614: E/AndroidRuntime(674):  at android.view.SurfaceView$3.onPreDraw(SurfaceView.java:171)
05-10 03:31:23.614: E/AndroidRuntime(674):  at android.view.ViewTreeObserver.dispatchOnPreDraw(ViewTreeObserver.java:590)
05-10 03:31:23.614: E/AndroidRuntime(674):  at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1596)
05-10 03:31:23.614: E/AndroidRuntime(674):  at android.view.ViewRootImpl.handleMessage(ViewRootImpl.java:2418)
05-10 03:31:23.614: E/AndroidRuntime(674):  at android.os.Handler.dispatchMessage(Handler.java:99)
05-10 03:31:23.614: E/AndroidRuntime(674):  at android.os.Looper.loop(Looper.java:137)
05-10 03:31:23.614: E/AndroidRuntime(674):  at android.app.ActivityThread.main(ActivityThread.java:4340)
05-10 03:31:23.614: E/AndroidRuntime(674):  at java.lang.reflect.Method.invokeNative(Native Method)
05-10 03:31:23.614: E/AndroidRuntime(674):  at java.lang.reflect.Method.invoke(Method.java:511)
05-10 03:31:23.614: E/AndroidRuntime(674):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
05-10 03:31:23.614: E/AndroidRuntime(674):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
05-10 03:31:23.614: E/AndroidRuntime(674):  at dalvik.system.NativeStart.main(Native Method)

这是我的代码:

package com.android.gs1;

import java.io.IOException;
import android.os.Bundle;
import android.os.Parcelable;
import android.app.Activity;
import android.content.Context;
import android.hardware.Camera;
import android.support.v4.view.PagerAdapter;
import android.support.v4.view.ViewPager;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.view.View;
import android.view.ViewGroup;
import android.widget.LinearLayout;
import android.widget.Toast;


public class MainActivity extends Activity {

ViewPager vp;
Camera mCamera;
SurfaceHolder mHolder;
static int j;
private vpAdapter myAdapter;
CameraPreview preview;

public static void passPageNumber(int i){
    j = i;
}
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);


    Toast.makeText(getApplicationContext(), "Swipe Left or Right to Select an Option", Toast.LENGTH_LONG).show();
    vp = (ViewPager) findViewById(R.id.viewpager);
    myAdapter = new vpAdapter();
    preview = new CameraPreview(getApplicationContext(), mCamera);
    ((LinearLayout) findViewById(R.id.preview)).addView(preview);
    vp.setAdapter(myAdapter);
}

private class CameraPreview extends SurfaceView implements SurfaceHolder.Callback{


    private final String TAG = null;


    public CameraPreview(Context context, Camera camera) {
        super(context);
        // TODO Auto-generated constructor stub
        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);
    }

    @Override
    public void surfaceChanged(SurfaceHolder holder, int format, int width,
            int height) {
        // TODO Auto-generated method stub
        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(TAG, "Error starting camera preview: " + e.getMessage());
            }
    }

    @Override
    public void surfaceCreated(SurfaceHolder holder) {
        // TODO Auto-generated method stub
        try {
            mCamera = Camera.open();
            mCamera.setPreviewDisplay(holder);
            mCamera.startPreview();
        } catch (IOException e) {
            Log.d(TAG, "Error setting camera preview: " + e.getMessage());
        }
    }

    @Override
    public void surfaceDestroyed(SurfaceHolder holder) {
        // TODO Auto-generated method stub

    }

}
private class vpAdapter extends PagerAdapter{

    @Override
    public int getCount() {
        // TODO Auto-generated method stub
        return 5;
    }

    @Override
    public boolean isViewFromObject(View view, Object object) {
        // TODO Auto-generated method stub
        return view == ((LinearLayout)object);
    }

    @Override
    public void destroyItem(ViewGroup container, int position, Object object) {
        // TODO Auto-generated method stub
        ((ViewPager)container).removeView((LinearLayout)object);
    }

    @Override
    public void finishUpdate(ViewGroup container) {
        // TODO Auto-generated method stub

    }


    @Override
    public Object instantiateItem(View container, int position) {
        // TODO Auto-generated method stub
        LayoutInflater inflater = (LayoutInflater)container.getContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        View v = null;

        switch(position){
        case 0:
            v = inflater.inflate(R.layout.first, null);
            break;
        case 1:
            v = inflater.inflate(R.layout.second, null);
            break;
        case 2:
            v = inflater.inflate(R.layout.third, null);
            break;
        case 3:
            v = inflater.inflate(R.layout.fourth, null);
            break;
        case 4:
            v = inflater.inflate(R.layout.fifth, null);
            break;
        }


        ((ViewPager)container).addView(v, 0);
        return v;
    }
    @Override
    public void startUpdate(ViewGroup container) {
        // TODO Auto-generated method stub

    }
    @Override
    public Parcelable saveState() {
        // TODO Auto-generated method stub
        return null;
    }

}
}

这是我的xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity" 
android:background="#545454" >

<android.support.v4.view.ViewPager
    android:id="@+android:id/viewpager"
    android:layout_width="0dip"
    android:layout_height="wrap_content"
    android:layout_weight="0.49" />
<LinearLayout
    android:id="@+id/preview"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content">
</LinearLayout>
</LinearLayout>

viewpager 还有五个 xml。它们看起来都像这样，但名称和 ID 不同。

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical"
 >

<ImageView
android:id="@+id/image1"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:adjustViewBounds="false"
android:contentDescription="@string/description_image_1"
android:scaleType="fitXY"
android:src="@drawable/first" />

</LinearLayout>

非常感谢

编辑:有人问我代码的最终工作版本。在这里:

public class MainActivity extends Activity {

ViewPager vp;
vpAdapter myAdapter;
Camera camera = null;
SurfaceHolder previewHolder = null;
private SurfaceView preview = null;
private boolean inPreview = false;
private boolean cameraConfigured = false;
public static String[] arrayURL;
public static boolean urlsPassed;
private View mContentView;
private View mLoadingView;

private int mShortAnimationDuration;


@SuppressWarnings("deprecation")
@SuppressLint("NewApi")
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    requestWindowFeature(Window.FEATURE_NO_TITLE);
    setContentView(R.layout.activity_main);
    Toast.makeText(getApplicationContext(), "Swipe Left or Right to Select an Option", Toast.LENGTH_SHORT).show();
    //NEW CODE

    mContentView = findViewById(R.id.content);
    mLoadingView = findViewById(R.id.loading_spinner);
    mContentView.setVisibility(View.GONE);
    mShortAnimationDuration = getResources().getInteger(
            android.R.integer.config_shortAnimTime);
    //NEW CODE
    preview=(SurfaceView)findViewById(R.id.preview);
    preview.setZOrderOnTop(false);
    previewHolder=preview.getHolder();
    previewHolder.addCallback(surfaceCallback);
    previewHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);

}
private void crossfade() {

    // Set the content view to 0% opacity but visible, so that it is visible
    // (but fully transparent) during the animation.
    mContentView.setAlpha(0f);
    mContentView.setVisibility(View.VISIBLE);

    // Animate the content view to 100% opacity, and clear any animation
    // listener set on the view.
    mContentView.animate()
            .alpha(1f)
            .setDuration(mShortAnimationDuration)
            .setListener(null);

    // Animate the loading view to 0% opacity. After the animation ends,
    // set its visibility to GONE as an optimization step (it won't
    // participate in layout passes, etc.)
    mLoadingView.animate()
            .alpha(0f)
            .setDuration(mShortAnimationDuration)
            .setListener(new AnimatorListenerAdapter() {
                @Override
                public void onAnimationEnd(Animator animation) {
                    mLoadingView.setVisibility(View.GONE);
                }
            });
}
    public static void assignURL(String[] urls){
    arrayURL = urls;
}

    public static void urlsPassed(boolean transfer){
        urlsPassed = transfer;
    }

@Override
  public void onResume() {
    super.onResume();
    camera=Camera.open();
}

 @Override
 public boolean onCreateOptionsMenu(Menu menu) {
  getMenuInflater().inflate(R.menu.main, menu);
  return true;
 }
@Override
  public void onPause() {
    if (inPreview) {
      camera.stopPreview();
    }

    camera.release();
    camera=null;
    inPreview=false;

    super.onPause();
  }

private Camera.Size getBestPreviewSize(int width, int height,Camera.Parameters parameters) {

    Camera.Size result=null;
    for (Camera.Size size : parameters.getSupportedPreviewSizes()) {
        if (size.width<=width && size.height<=height) {
            if (result==null) {
                result=size;
            }
            else {
                int resultArea=result.width*result.height;
                int newArea=size.width*size.height;

                if (newArea>resultArea) {
                    result=size;
                }
            }
        }
    }

    return(result);
}
private void initPreview(int width, int height) {
    if (camera!=null && previewHolder.getSurface()!=null) {
      try {
        camera.setPreviewDisplay(previewHolder);
      }
      catch (Throwable t) {
        Log.e("PreviewDemo-surfaceCallback",
              "Exception in setPreviewDisplay()", t);
        Toast
          .makeText(MainActivity.this, t.getMessage(), Toast.LENGTH_LONG)
          .show();
      }

      if (!cameraConfigured) {
        Camera.Parameters parameters=camera.getParameters();
        Camera.Size size=getBestPreviewSize(width, height,
                                            parameters);

        if (size!=null) {
          parameters.setPreviewSize(size.width, size.height);
          camera.setParameters(parameters);
          cameraConfigured=true;
        }
      }
    }
  }

 private void startPreview() {
        if (cameraConfigured && camera!=null) {
          camera.startPreview();
          inPreview=true;
          crossfade();
          if(urlsPassed){
            myAdapter = new vpAdapter(this,  arrayURL);
            vp = (ViewPager) findViewById(R.id.viewpager);
            vp.setAdapter(myAdapter);
            vp.setCurrentItem(0);
          }
        }
      }

 SurfaceHolder.Callback surfaceCallback=new SurfaceHolder.Callback() {
        @Override
        public void surfaceCreated(SurfaceHolder holder) {
          // no-op -- wait until surfaceChanged()
        }

        @Override
        public void surfaceChanged(SurfaceHolder holder, int format, int width,int height) {


          Camera.Parameters parameters = camera.getParameters();
          parameters.setFocusMode(Camera.Parameters.FOCUS_MODE_AUTO);
          camera.setParameters(parameters);
          initPreview(width, height);
          startPreview();
          camera.autoFocus(null);
        }

        @Override
        public void surfaceDestroyed(SurfaceHolder holder) {
          // no-op
        }
      };

}

Answer 1

对于 future 与此类问题作斗争的人们。我找到了解决方案:

首先，无论您在预览顶部设置什么，都必须在布局中放置在 SurfaceView 之后。例如:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    tools:context=".MainActivity" 
    android:background="#ffff">

    <android.view.SurfaceView
        android:id="@+id/preview"
        android:layout_width="4978dp"
        android:layout_height="5131dp">
    </android.view.SurfaceView>

    <android.support.v4.view.ViewPager
        android:id="@+android:id/viewpager"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"/>
</RelativeLayout>

其次，在Java文件中，SurfaceView必须setZOrderOnTop为false。例如:

SurfaceView preview=(SurfaceView)findViewById(R.id.preview);
preview.setZOrderOnTop(false);

第三，设置调用camera中的startPreview函数后位于CameraPreview顶部的layout。

就是这样。