尝试让一个简单的相机应用程序工作

Question

我是 Android 应用程序开发的初学者。我正在掌握它的窍门，我已经阅读了很多教程，但我仍然无法让相机工作。基本上我想做的是拍照，将图像存储在应用程序内部，然后显示该图像以（稍后）能够在其上绘图。我现在不担心绘图部分，因为我仍然收到 SetOnClickListener 的错误...这是代码。

import android.hardware.Camera;
import android.net.Uri; 
import android.os.Environment;
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.FrameLayout;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.text.SimpleDateFormat;
import java.util.Date;


public class MainActivity extends ActionBarActivity {

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

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

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

}
private Camera.PictureCallback mPicture = new Camera.PictureCallback() {

    @Override
    public void onPictureTaken(byte[] data, Camera camera) {

        File pictureFile = getOutputMediaFile(MEDIA_TYPE_IMAGE);
        if (pictureFile == null){
           // Log.d("erre", "Error creating media file, check storage permissions: " +
             //       getMessage());
            return;
        }

        try {
            FileOutputStream fos = new FileOutputStream(pictureFile);
            fos.write(data);
            fos.close();
        } catch (FileNotFoundException e) {
            Log.d("erra", "File not found: " + e.getMessage());
        } catch (IOException e) {
            Log.d("erra", "Error accessing file: " + e.getMessage());
        }
    }
};


@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;
    }

    return super.onOptionsItemSelected(item);
}
/** A safe way to get an instance of the Camera object. */
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
}



// Add a listener to the Capture button
Button captureButton = (Button) findViewById(R.id.button_capture);

captureButton.setOnClickListener(new View.OnClickListener() {

    @Override
    public void onClick(View v) {
        Camera mCamera = getCameraInstance();
        // get an image from the camera
        mCamera.takePicture(null, null, mPicture);
    }
}
);

public static final int MEDIA_TYPE_IMAGE = 1;
public static final int MEDIA_TYPE_VIDEO = 2;

/** Create a file Uri for saving an image or video */
private static Uri getOutputMediaFileUri(int type){
    return Uri.fromFile(getOutputMediaFile(type));
}

/** Create a File for saving an image or video */
private static File getOutputMediaFile(int type){
    // To be safe, you should check that the SDCard is mounted
    // using Environment.getExternalStorageState() before doing this.

    File mediaStorageDir = new File(Environment.getExternalStoragePublicDirectory(
            Environment.DIRECTORY_PICTURES), "MyCameraApp");
    // This location works best if you want the created images to be shared
    // between applications and persist after your app has been uninstalled.

    // Create the storage directory if it does not exist
    if (! mediaStorageDir.exists()){
        if (! mediaStorageDir.mkdirs()){
            Log.d("MyCameraApp", "failed to create directory");
            return null;
        }
    }

    // Create a media file name
    String timeStamp = new SimpleDateFormat("yyyyMMdd_HHmmss").format(new Date());
    File mediaFile;
    if (type == MEDIA_TYPE_IMAGE){
        mediaFile = new File(mediaStorageDir.getPath() + File.separator +
                "IMG_"+ timeStamp + ".jpg");
    } else if(type == MEDIA_TYPE_VIDEO) {
        mediaFile = new File(mediaStorageDir.getPath() + File.separator +
                "VID_"+ timeStamp + ".mp4");
    } else {
        return null;
    }

    return mediaFile;
}

}

Answer 1

只需移动这部分：

// Add a listener to the Capture button
Button captureButton = (Button) findViewById(R.id.button_capture);

captureButton.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View v) {
        Camera mCamera = getCameraInstance();
        // get an image from the camera
        mCamera.takePicture(null, null, mPicture);
    }
}
);

进入你的 onCreate() 函数，在它的末尾。然后它应该工作。需要在Activities的onCreate中找到views/setup点击事件。

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