Question

我是Android的新手程序员我试图通过点击按钮启动Android中的相机预览。我正在尝试直接访问相机硬件，而不是使用默认的相机应用程序。这是我写的代码

import android.app.Activity;
import android.hardware.Camera;
import android.os.Bundle;
import android.util.Log;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;

public class CameraHandler extends Activity {
    private SurfaceView sv = null;
    private SurfaceHolder previewHolder = null;

    private Button btnStop;
    private Button btnStart;
    private Camera camera = null;

    public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.cameraview);

    // Get the surface view from main layout
    sv = (SurfaceView) findViewById(R.id.cameraSurface);

    // Get the buttons from XML
    btnStart = (Button) findViewById(R.id.startButton);
    btnStop = (Button) findViewById(R.id.stopButton);



    btnStart.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {
        // TODO Auto-generated method stub

        SurfaceHolder.Callback surfaceCallBack = new SurfaceHolder.Callback() {

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

            camera.release();
            camera = null;
            }

            @Override
            public void surfaceCreated(SurfaceHolder holder) {
            // TODO Auto-generated method stub
            camera = Camera.open();
            try {
                camera.setPreviewDisplay(previewHolder);
            } catch (Throwable t) {
                // TODO Auto-generated catch block
                Log.e("PreviewDemo-surfaceCallback",
                    "Exception in setPreviewDisplay()", t);
                Toast.makeText(CameraHandler.this, t.getMessage(),
                    Toast.LENGTH_LONG).show();
            }
            }

            @Override
            public void surfaceChanged(SurfaceHolder holder,
                int format, int width, int height) {
            // TODO Auto-generated method stub
            Camera.Parameters parameters = camera.getParameters();
            parameters.setPreviewSize(width, height);
            camera.setParameters(parameters);
            camera.startPreview();

            }
        };

        // Get the surface holder from the surface view
        previewHolder = sv.getHolder();

        // Now add these call backs
        previewHolder.addCallback(surfaceCallBack);
        previewHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
        }
    });

    btnStop.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {
        // TODO Auto-generated method stub
        camera.stopPreview();
        }
    });
    }

}

正如您所看到的，我从SurfaceView中获取表面支架，在单击开始按钮时添加回调。由于某种原因，没有调用SufraceHolder回调。但是，如果我将整个代码直接放在onCreate函数中，它可以正常工作，即在启动活动时启动相机预览。我在这里错过了什么吗？

先谢谢

Answer 1

单击按钮时已创建SurfaceView。因此，surfaceCreated()可能不会被调用。

无法启动摄像头单击按钮时预览

1 个答案: