所以我想构建一个使用相机并在内部（在应用程序内）保存图像的Android应用程序，然后显示刚刚在下一个活动中拍摄的图片......但是我在输出图像时遇到问题。我相信我已经正确保存了图片......但我不确定如何读取数据。我查看了许多教程，但无法找到我应该在下一个活动中放置哪些方法来显示图像。以下是主要活动的代码：
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 android.widget.Toast;
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);
// 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);
}
}
);
}
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("Logtag:", "Error creating media file, check storage permissions: "
);
return;
}
try {
FileOutputStream fos = new FileOutputStream(pictureFile);
fos.write(data);
fos.close();
} catch (FileNotFoundException e) {
Log.d("Logtag:", "File not found: " + e.getMessage());
} catch (IOException e) {
Log.d("Logtag:", "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 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)
Toast.makeText(getApplicationContext(), "Camera is not available (in use or does not exist)",
Toast.LENGTH_LONG).show();
}
return c; // returns null if camera is unavailable
}
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 locat ion 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("Logtag", "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;
}
}
答案 0 :(得分：0)
将图像文件的路径或uri传递给intent中的其他活动。扩展包括ImageView的布局。使用BitmapFactory解码图像文件。在ImageView上设置生成的位图。
答案 1 :(得分：0)
我知道这可能不是您正在寻找的答案，但您是否考虑过使用图书馆来显示您刚刚拍摄的照片？
我通常使用毕加索，我很高兴。 http://square.github.io/picasso/
如果您有图像路径和视图以显示图像，您基本上可以在一行代码中显示图像，如：
Picasso.with(context).load(pictureFile.getAbsolutePath()).into(view);
答案 2 :(得分：0)
您需要解码文件数据。为了节省内存，请将位图缩小到适合您的显示的位置（maxSize）
public static Bitmap decodeFile(File f, final int maxSize) {
Bitmap b = null;
// Decode image size
BitmapFactory.Options o = new BitmapFactory.Options();
o.inJustDecodeBounds = true;
FileInputStream fis = null;
try {
fis = new FileInputStream(f);
BitmapFactory.decodeStream(fis, null, o);
fis.close();
int scale = 1;
if (o.outHeight > maxSize || o.outWidth > maxSize) {
scale = (int) Math.pow(2, (int) Math.round(Math.log(maxSize / (double) Math.max(o.outHeight, o.outWidth)) / Math.log(0.5)));
}
// Decode with inSampleSize
BitmapFactory.Options o2 = new BitmapFactory.Options();
o2.inSampleSize = scale;
fis = new FileInputStream(f);
b = BitmapFactory.decodeStream(fis, null, o2);
} catch (Exception e) {
Log.e(ImageUtils.TAG, "Error processing bitmap", e);
} finally {
FileUtil.closeQuietly(fis);
}
return b;
}
然后可以在ImageView中使用位图
e.g
mImageView.setImageBitmap(bitmap);