我的程序的目标是（至少在这个阶段）从玻璃上获取照片然后在屏幕上显示（我正在使用沉浸式）。
我的班级（当然extends Activity）有以下内容：
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_picture_analysis);
Intent getTheImageIntent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
startActivityForResult(getTheImageIntent, 25);
}
启动相机。用户接收并接受照片后，会调用我的public void onActivityResult方法
public void onActivityResult(int requestCode, int resultCode, Intent data) {
// A bunch of debug logging that I inserted
Log.d("glass", "got a pic!!");
Log.d("glass", String.valueOf(resultCode));
Log.d("glass", String.valueOf(resultCode==RESULT_OK));
if (data.getExtras() != null && requestCode == 25) {
Log.d("glass", "in the if");
//Create an instance of bundle and get the returned data
Bundle extras = data.getExtras();
final String pathToImage = (String) extras.get("picture_file_path");
for (String key : extras.keySet()) {
Object value = extras.get(key);
Log.d("glass", String.format("%s %s (%s)", key,
value.toString(), value.getClass().getName()));
}
FileObserver observer = new FileObserver(pathToImage) {
@Override
public void onEvent(int event, String path) {
Log.d("glass", "we observed an event");
if (event == FileObserver.CLOSE_WRITE || event==FileObserver.CLOSE_NOWRITE) {
Bitmap thePicUnscaled = BitmapFactory.decodeFile(pathToImage);
Log.d("glass", "observer found a close_write event");
Bitmap thePic = Bitmap.createScaledBitmap(thePicUnscaled,
getResources().getDisplayMetrics().widthPixels,
getResources().getDisplayMetrics().heightPixels,
true);
ImageView imgView = (ImageView) findViewById(R.id.thePictureView);
imgView.setImageBitmap(thePic);
}
}
};
observer.startWatching();
Log.d("glass","observer started watching");
} else {
Log.d("glass", "There were no extras passed with intent in onActivityResult");
}
}
现在我的问题是虽然我已经调用了文件观察者，但它实际上从未观察到变化。即使每次有事件我都应该记录Log.d("glass", "we observed an event");，但它永远不会记录。我的logcat（为我的标签过滤）看起来像：
05-16 14:27:31.007 4976-4976/com.nkhosla.glasstest.app D/dalvikvm﹕ Late-enabling CheckJNI
05-16 14:27:31.007 4976-4976/com.nkhosla.glasstest.app D/dalvikvm﹕ Try to disable coredump for pid 4976
05-16 14:27:31.007 4976-4976/com.nkhosla.glasstest.app D/dalvikvm﹕ Process 4976 nice name: com.nkhosla.glasstest.app
05-16 14:27:31.007 4976-4976/com.nkhosla.glasstest.app D/dalvikvm﹕ Extra Options: not specified
05-16 14:27:32.031 4976-4976/com.nkhosla.glasstest.app D/OpenGLRenderer﹕ Enabling debug mode 0
05-16 14:27:35.625 4976-4976/com.nkhosla.glasstest.app D/glass﹕ got a pic!!
05-16 14:27:35.625 4976-4976/com.nkhosla.glasstest.app D/glass﹕ -1
05-16 14:27:35.625 4976-4976/com.nkhosla.glasstest.app D/glass﹕ true
05-16 14:27:35.625 4976-4976/com.nkhosla.glasstest.app D/glass﹕ in the if
05-16 14:27:35.625 4976-4976/com.nkhosla.glasstest.app D/glass﹕ thumbnail_file_path /storage/emulated/0/thumbnail_cache/t_thumb_20140516_142732_930.jpg (java.lang.String)
05-16 14:27:35.625 4976-4976/com.nkhosla.glasstest.app D/glass﹕ picture_file_path /storage/emulated/0/DCIM/Camera/20140516_142732_930.jpg (java.lang.String)
05-16 14:27:35.640 4976-4976/com.nkhosla.glasstest.app D/glass﹕ observer started watching
我已经尝试在观察者开始观看之后立即访问该文件，但如果我尝试访问使用NullPointerException
Bitmap thePicUnscaled = BitmapFactory.decodeFile(pathToImage);
我让文件观察者坐了一下手表至少5秒左右，这是闪存写入速度的永恒。我不知道我的问题是什么。
作为参考，我的layout.xml：
<RelativeLayout 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"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
android:paddingBottom="@dimen/activity_vertical_margin"
tools:context="com.nkhosla.glasstest.app.PictureAnalysis">
<ImageView
android:layout_height="fill_parent"
android:layout_width="fill_parent"
android:id="@+id/thePictureView"
android:maxHeight="300dp"
android:maxWidth="640dp"
android:scaleType="centerCrop"
android:adjustViewBounds="true"/>
</RelativeLayout>
答案 0 :(得分：1)
如果你在使用Camera Intent时唯一感兴趣的是图片的缩小版本，那么你应该使用CameraManager#EXTRA_THUMBNAIL_FILE_PATH代替完整图片，原因如下：
如果需要完整映像，FileObserver应该观察文件的父目录，而不是文件本身。 以下是我们在Developer's Guide中提供的代码段：
private static final int TAKE_PICTURE_REQUEST = 1;
private void takePicture() {
Intent intent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
startActivityForResult(intent, TAKE_PICTURE_REQUEST);
}
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
if (requestCode == TAKE_PICTURE_REQUEST && resultCode == RESULT_OK) {
String picturePath = data.getStringExtra(
CameraManager.EXTRA_PICTURE_FILE_PATH);
processPictureWhenReady(picturePath);
}
super.onActivityResult(requestCode, resultCode, data);
}
private void processPictureWhenReady(final String picturePath) {
final File pictureFile = new File(picturePath);
if (pictureFile.exists()) {
// The picture is ready; process it.
} else {
// The file does not exist yet. Before starting the file observer, you
// can update your UI to let the user know that the application is
// waiting for the picture (for example, by displaying the thumbnail
// image and a progress indicator).
final File parentDirectory = pictureFile.getParentFile();
FileObserver observer = new FileObserver(parentDirectory.getPath(),
FileObserver.CLOSE_WRITE | FileObserver.MOVED_TO) {
// Protect against additional pending events after CLOSE_WRITE
// or MOVED_TO is handled.
private boolean isFileWritten;
@Override
public void onEvent(int event, String path) {
if (!isFileWritten) {
// For safety, make sure that the file that was created in
// the directory is actually the one that we're expecting.
File affectedFile = new File(parentDirectory, path);
isFileWritten = affectedFile.equals(pictureFile);
if (isFileWritten) {
stopWatching();
// Now that the file is ready, recursively call
// processPictureWhenReady again (on the UI thread).
runOnUiThread(new Runnable() {
@Override
public void run() {
processPictureWhenReady(picturePath);
}
});
}
}
}
};
observer.startWatching();
}
}