Question

我是android新手，请原谅我的无知。我正在尝试在主要活动中添加一个按钮，单击此按钮会将应用程序转换为摄像机视图。

主要活动代码：

package com.cerezaenterprises.swiftversionuno;
import android.content.Intent;
import android.support.v7.app.ActionBarActivity;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;

public class MainActivity extends ActionBarActivity  {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }
    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is   present.
        getMenuInflater().inflate(R.menu.menu_main, 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();
        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }
        super.onOptionsItemSelected(item);
        return true;
    }
    private Button button;
    button = (Button) findViewById(R.id.button)*****
    private void setupMessageButton() {
        Button button = (Button) findViewById(R.id.button);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent(MainActivity.this, CameraView1.class);
                startActivity(intent);
            }
        });
    }
}

我有一个问题，它是星号，说明第1名:(未知课程：＆＃39;按钮＆＃39;）第二个:(无效的方法声明）＆＃39; findViewById＆＃39; 第3名:(未知类R.id.button）

activity_main.xml中：

<RelativeLayout   xmlns:android="http://schemas.android.com/apk/res/android"
    android:id= "@+id/rootRL"
    android:orientation="vertical"
    android:layout_width = "fill_parent"
    android:layout_height = "fill_parent"
    android:background = "@drawable/background">
    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="New Button"
        android:id="@+id/button"
        android:layout_alignParentBottom="true"
        android:layout_centerHorizontal="true"
        android:layout_marginBottom="64dp" />
</RelativeLayout>

我的上一个问题已解决，解决了我的问题后，更新了代码。

package com.cerezaenterprises.swiftversionuno;


 import android.content.Intent;
 import android.support.v7.app.ActionBarActivity;
 import android.support.v7.app.AppCompatActivity;
 import android.os.Bundle;
 import android.view.Menu;
 import android.view.MenuItem;
 import android.view.View;
 import android.widget.Button;



 public class MainActivity extends ActionBarActivity  {
 private Button button;
     @Override
      protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_main);
         button = (Button) findViewById(R.id.button);
         button.setOnClickListener(new View.OnClickListener() {
          @Override
          public void onClick(View v) {
            Intent intent = new Intent(MainActivity.this, CameraView1.class);
            startActivity(intent);
          }
         });
     }

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

         //noinspection SimplifiableIfStatement
         if (id == R.id.action_settings) {
             return true;
         }

         super.onOptionsItemSelected(item);

         return true;
       }
 }

修复第一个问题，然后点击我的相机按钮，我的应用程序崩溃了，日志猫说'＃34;没有零参数构造函数＆＃34;。有谁知道如何解决这个问题？我被卡住了。这是我的CameraView1代码：

package com.cerezaenterprises.swiftversionuno;

import java.io.IOException;
import java.util.List;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.PixelFormat;
import android.hardware.Camera;
import android.hardware.Camera.Size;
import android.util.Log;
import android.view.SurfaceHolder;
import android.view.SurfaceView;

import static java.lang.System.loadLibrary;

/**
 * Extention of SurfaceView which starts a camera preview and decode video
 * content on the native side.
 */
public class CameraView1 extends SurfaceView implements SurfaceHolder.Callback,
        Camera.PreviewCallback {
    private static final String TAG = "LiveCamera";


    static {
        loadLibrary("LiveCamera");

    }

    public native void decode(Bitmap pTarget, byte[] pSource);

    private Camera mCamera;
    private byte[] mVideoSource;
    private Bitmap mBackBuffer;
    private Paint mPaint;

    public CameraView1(Context context) {
        super(context);

        // Registers current class so that it listens to surface
        // event (creation, destruction and changes).
        getHolder().addCallback(this);
        // Clears the flag keeping the surface from getting drawn.
        // Necessary when not drawing from a thread.
        setWillNotDraw(false);
    }

    public void surfaceCreated(SurfaceHolder holder) {
        try {
            // Acquires the default camera.
            mCamera = Camera.open();
            // Sets landscape mode to avoid complications related to
            // screen orientation handling.
            mCamera.setDisplayOrientation(0);
            // Registers callbacks. Automatic preview is deactivated
            // as we want to process data ourself (in a buffer).
            mCamera.setPreviewDisplay(null);
            mCamera.setPreviewCallbackWithBuffer(this);
        } catch (IOException eIOException) {
            mCamera.release();
            mCamera = null;
            throw new IllegalStateException();
        }
    }

    public void surfaceChanged(SurfaceHolder pHolder, int pFormat, int pWidth,
                               int pHeight) {
        mCamera.stopPreview();

        // Finds a suitable resolution.
        Size lSize = findBestResolution(pWidth, pHeight);

        // Prepares video source and back buffers.
        PixelFormat lPixelFormat = new PixelFormat();
        PixelFormat.getPixelFormatInfo(mCamera.getParameters()
                .getPreviewFormat(), lPixelFormat);
        int lSourceSize = lSize.width * lSize.height
                * lPixelFormat.bitsPerPixel / 8;
        mVideoSource = new byte[lSourceSize];
        mBackBuffer = Bitmap.createBitmap(lSize.width, lSize.height,
                Bitmap.Config.ARGB_8888);

        // Set-up camera size and video format. YCbCr_420_SP
        // should be the default on Android anyway.
        Camera.Parameters lParameters = mCamera.getParameters();
        lParameters.setPreviewSize(lSize.width, lSize.height);
        lParameters.setPreviewFormat(PixelFormat.YCbCr_420_SP);
        mCamera.setParameters(lParameters);

        // Starts receiving pictures from the camera.
        mCamera.addCallbackBuffer(mVideoSource);
        mCamera.startPreview();
    }

    private Size findBestResolution(int pWidth, int pHeight) {
        List<Size> lSizes = mCamera.getParameters().getSupportedPreviewSizes();
        // Finds the biggest resolution which fits the screen.
        // Else, returns the first resolution found.
        Size lSelectedSize = mCamera.new Size(0, 0);
        for (Size lSize : lSizes) {
            if ((lSize.width <= pWidth) && (lSize.height <= pHeight)
                    && (lSize.width >= lSelectedSize.width)
                    && (lSize.height >= lSelectedSize.height)) {
                lSelectedSize = lSize;
            }
        }
        // Previous code assume that there is a preview size smaller
        // than screen size. If not, hopefully the Android API
        // guarantees that at least one preview size is available.
        if ((lSelectedSize.width == 0) || (lSelectedSize.height == 0)) {
            lSelectedSize = lSizes.get(0);
        }
        Log.d(TAG, "findBestResolution: " + lSelectedSize.width + ","
                + lSelectedSize.height);
        return lSelectedSize;
    }

    public void surfaceDestroyed(SurfaceHolder holder) {
        // Releases camera which is a shared resource.
        if (mCamera != null) {
            mCamera.stopPreview();
            mCamera.release();
            // These variables can take a lot of memory. Gets rid of
            // them as fast as we can.
            mCamera = null;
            mVideoSource = null;
            mBackBuffer = null;
        }
    }

    public void onPreviewFrame(byte[] pData, Camera pCamera) {
        // New data has been received from camera. Processes it and
        // requests surface to be redrawn right after.
        decode(mBackBuffer, pData);
        invalidate();
    }

    @Override
    protected void onDraw(Canvas pCanvas) {
        if (mCamera != null) {
            // Draws resulting image at screen origin.
            pCanvas.drawBitmap(mBackBuffer, 0, 0, mPaint);
            // Enqueues buffer again to get next image.
            mCamera.addCallbackBuffer(mVideoSource);
        }
    }
}

这是我的Log Cat从崩溃开始：

 --------- beginning of crash
07-29 11:33:36.336    2074-2074/com.cerezaenterprises.swiftversionuno E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: com.cerezaenterprises.swiftversionuno, PID: 2074
    java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.cerezaenterprises.swiftversionuno/com.cerezaenterprises.swiftversionuno.CameraView1}: java.lang.InstantiationException: class com.cerezaenterprises.swiftversionuno.CameraView1 has no zero argument constructor
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2236)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2390)
            at android.app.ActivityThread.access$800(ActivityThread.java:151)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5257)
            at java.lang.reflect.Method.invoke(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:372)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
     Caused by: java.lang.InstantiationException: class com.cerezaenterprises.swiftversionuno.CameraView1 has no zero argument constructor
            at java.lang.Class.newInstance(Class.java:1597)
            at android.app.Instrumentation.newActivity(Instrumentation.java:1066)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2226)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2390)
            at android.app.ActivityThread.access$800(ActivityThread.java:151)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5257)
            at java.lang.reflect.Method.invoke(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:372)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
     Caused by: java.lang.NoSuchMethodException: <init> []
            at java.lang.Class.getConstructor(Class.java:531)
            at java.lang.Class.getDeclaredConstructor(Class.java:510)
            at java.lang.Class.newInstance(Class.java:1595)
            at android.app.Instrumentation.newActivity(Instrumentation.java:1066)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2226)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2390)
            at android.app.ActivityThread.access$800(ActivityThread.java:151)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5257)
            at java.lang.reflect.Method.invoke(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:372)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)

有谁知道如何解决这个问题？我被卡住了。

Answer 1

package com.cerezaenterprises.swiftversionuno;


 import android.content.Intent;
 import android.support.v7.app.ActionBarActivity;
 import android.support.v7.app.AppCompatActivity;
 import android.os.Bundle;
 import android.view.Menu;
 import android.view.MenuItem;
 import android.view.View;
 import android.widget.Button;



 public class MainActivity extends ActionBarActivity  {
 private Button button;
     @Override
      protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_main);
         button = (Button) findViewById(R.id.button);
         button.setOnClickListener(new View.OnClickListener() {
          @Override
          public void onClick(View v) {
            Intent intent = new Intent(MainActivity.this, CameraView1.class);
            startActivity(intent);
          }
         });
     }

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

         //noinspection SimplifiableIfStatement
         if (id == R.id.action_settings) {
             return true;
         }

         super.onOptionsItemSelected(item);

         return true;
       }
 }

未知类：＆＃39;按钮＆＃39; ＆安培;无效的方法取消; findViewById所需的返回类型

主要活动代码：

activity_main.xml中：

1 个答案: