Java cannot open loop without calling Create a handler within the thread of prepare()
•
Java
I've seen most of the related problems, but I can't find any solution
This is my code. I don't know what I did wrong
static class NamedFile {
public File f;
public String name;
public String ext;
public String path;
public BitmapDrawable icon;
public NamedFile (File file) {
f = file;
name = f.getName();
if (f.isFile()) {
if (name.indexOf('.') != -1) {
ext = name.substring(name.lastIndexOf('.') + 1).trim().toLowerCase();
} else {
ext = "unkNown";
}
}
path = f.getAbsolutePath();
if (ext == null) {
icon = mFolderIcon;
} else {
BitmapDrawable i = icons.get(ext);
if (i == null) {
try {
int rid = R.drawable.class.getField(ext).getInt(R.drawable.class);
icons.put(ext,new BitmapDrawable(Bitmap.createScaledBitmap(BitmapFactory.decodeResource(res,rid,mOpts),iconSize,false)));
icon = icons.get(ext);
} catch (Exception e1) {}
} else {
icon = i;
}
}/* else if (ext.equals("jpeg") || ext.equals("jpg") || ext.equals("bmp") || ext.equals("gif") || ext.equals("png")) {
Bitmap b = BitmapFactory.decodeFile(path,mOpts);
if (b != null) {
icon = new BitmapDrawable(Bitmap.createScaledBitmap(b,false));
}
}*/
if (ext != null && (ext.equals("jpeg") || ext.equals("jpg") || ext.equals("bmp") || ext.equals("gif") || ext.equals("png"))) {
/*
Bitmap b = BitmapFactory.decodeFile(path,false));
}
*/
final Handler handler = new Handler() {
@Override
public void handleMessage(Message message) {
HashMap<String,Object> m = ((HashMap<String,Object>)message.obj);
sendThumbnail ((String)m.get("path"),(byte[])m.get("data"));
}
};
Thread thread = new Thread() {
public void writeInt (byte[] buff,int pos,int value) {
buff[pos] = (byte)(value >>> 24);
buff[pos + 1] = (byte)(value >>> 16);
buff[pos + 2] = (byte)(value >>> 8);
buff[pos + 3] = (byte)value;
}
@Override
public void run() {
try {
Bitmap b = BitmapFactory.decodeFile(path,mOpts);
if (b.getHeight() > 256 || b.getWidth() > 256) {
float r;
if (b.getHeight() > b.getWidth()) {
r = 128f / b.getHeight();
} else {
r = 128f / b.getWidth();
}
b = Bitmap.createScaledBitmap(b,(int)(r * b.getWidth()),(int)(r * b.getHeight()),false);
byte[] buffer = new byte[b.getWidth() * b.getHeight() * 4 + 8];
writeInt (buffer,b.getWidth());
writeInt (buffer,4,b.getHeight());
int i = 8;
for (int y = 0; y < b.getHeight(); y ++) {
for (int x = 0; x < b.getWidth(); x ++) {
writeInt (buffer,i,b.getPixel(x,y));
i += 4;
}
}
HashMap<String,Object> msg = new HashMap<String,Object>();
msg.put("path",path);
msg.put("data",buffer);
Message message = handler.obtainMessage(1,msg);
handler.sendMessage(message);
}
} catch (Exception e) {
sendLog (e.toString());
}
}
};
thread.start();
}
if (icon == null) {
icon = mFileIcon;
}
}
public NamedFile () {
}
public NamedFile simpleClone () {
final NamedFile nf = new NamedFile();
nf.name = name;
nf.ext = ext;
nf.path = path;
return nf;
}
}
It is nested in the if statement in the constructor of the static class, which is located in the public class extending listactivity I'm new to Java
Error:
05-01 20:21:58.810: E/AndroidRuntime(584): Uncaught handler: thread AsyncTask #1 exiting due to uncaught exception 05-01 20:21:58.830: E/AndroidRuntime(584): java.lang.RuntimeException: An error occured while executing doInBackground() 05-01 20:21:58.830: E/AndroidRuntime(584): at android.os.AsyncTask$3.done(AsyncTask.java:200) 05-01 20:21:58.830: E/AndroidRuntime(584): at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:273) 05-01 20:21:58.830: E/AndroidRuntime(584): at java.util.concurrent.FutureTask.setException(FutureTask.java:124) 05-01 20:21:58.830: E/AndroidRuntime(584): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:307) 05-01 20:21:58.830: E/AndroidRuntime(584): at java.util.concurrent.FutureTask.run(FutureTask.java:137) 05-01 20:21:58.830: E/AndroidRuntime(584): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1068) 05-01 20:21:58.830: E/AndroidRuntime(584): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:561) 05-01 20:21:58.830: E/AndroidRuntime(584): at java.lang.Thread.run(Thread.java:1096) 05-01 20:21:58.830: E/AndroidRuntime(584): Caused by: java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare() 05-01 20:21:58.830: E/AndroidRuntime(584): at android.os.Handler.<init>(Handler.java:121) 05-01 20:21:58.830: E/AndroidRuntime(584): at greg.projects.FileTransfer.FileTransferActivity$NamedFile$1.<init>(FileTransferActivity.java:588) 05-01 20:21:58.830: E/AndroidRuntime(584): at greg.projects.FileTransfer.FileTransferActivity$NamedFile.<init>(FileTransferActivity.java:588) 05-01 20:21:58.830: E/AndroidRuntime(584): at greg.projects.FileTransfer.FileTransferActivity$GesturesLoadTask.doInBackground(FileTransferActivity.java:489) 05-01 20:21:58.830: E/AndroidRuntime(584): at greg.projects.FileTransfer.FileTransferActivity$GesturesLoadTask.doInBackground(FileTransferActivity.java:1) 05-01 20:21:58.830: E/AndroidRuntime(584): at android.os.AsyncTask$2.call(AsyncTask.java:185) 05-01 20:21:58.830: E/AndroidRuntime(584): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305) 05-01 20:21:58.830: E/AndroidRuntime(584): ... 4 more
(filetransferactivity. Java: 588 is the final handler = new handler() {)
Solution
Handler is basically a callback class. When you send it some form of message, Android will use it to run code asynchronously In order for the handler to receive and process messages in a separate thread of the UI thread, it must keep the thread open This is where the looper class comes in As in the page example, loop. 0 is called at the top of the run () method Prepare (), then call looper. At the bottom loop(). The thread will remain open until you explicitly destroy it In order to destroy the looper thread, you must have a call looper in the thread class getMyLooper(). The method of quit()
An example thread class would look like this:
class LooperThread extends Thread {
public Handler mHandler;
private volatile Looper mMyLooper;
public void run() {
Looper.prepare();
mHandler = new Handler() {
public void handleMessage(Message msg) {
// process incoming messages here
}
};
mMyLooper = Looper.getMyLooper();
Looper.loop();
}
public void killMe(){
mMyLooper.quit();
}
}
The thread runs normally by creating a new object
LooperThread myLooperThread = new LooperThread();
Keep a reference to it Then call:
myLooperThread.killMe();
Whenever you want the thread to die This is usually in the onpause(), onstop() or ondestroy() methods of an activity
Note that when the activity is closed, threads of this nature will remain open, so you must terminate them before the user exits
The content of this article comes from the network collection of netizens. It is used as a learning reference. The copyright belongs to the original author.
THE END
二维码