我遇到了AsyncTasks的问题。 我在onCreate（）
中有这个new ProgressTask().execute();
这是我的任务：
private class ProgressTask extends AsyncTask<String, Integer, Boolean> {
private ProgressDialog dialog;
public ProgressTask() {
//dialog = new ProgressDialog(getBaseContext());
}
/** progress dialog to show user that the backup is processing. */
/** application context. */
private Context context;
protected void onPreExecute() {
dialog = new ProgressDialog(getBaseContext());
dialog.setTitle("Loading connection...");
dialog.setMessage("Loading...");
dialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
dialog.setMax(100);
dialog.setProgress(0);
dialog.show();
}
@Override
protected void onPostExecute(final Boolean success) {
if (dialog.isShowing()) {
dialog.dismiss();
}
if (success) {
Toast.makeText(context, "OK", Toast.LENGTH_LONG).show();
} else {
Toast.makeText(context, "Error", Toast.LENGTH_LONG).show();
}
}
protected Boolean doInBackground(final String... args) {
try{
//Get device ID
publishProgress(0);
loading.setMessage("Getting device ID...");
try {
getDeviceId();
} catch (Exception ex) {
ErrorMessage("Couldn't get device ID");
ErrorAlert += "Error 101: Couldn't get device ID\n";
}
Thread.sleep(2000);
publishProgress(20);
//Open connection
loading.setMessage("Opening connection...");
try {
openConnection();
} catch (IOException ex) {
ErrorMessage("Couldn't open connection");
ErrorAlert += "Error 102: Couldn't open connection\n";
}
Thread.sleep(2000);
publishProgress(40);
//Testing connection
loading.setMessage("Testing connection...");
if (!mmSocket.isConnected()) {
ErrorMessage("Test failed!");
ErrorAlert += "Error 103: Test failed!\n";
}
Thread.sleep(2000);
publishProgress(60);
//Calibrate sensors
loading.setMessage("Calibrating sensors...");
try {
sendCommand("c");
} catch (IOException ex) {
ErrorMessage("Couldn't calibrate sensors");
ErrorAlert += "Error 104: Couldn't calibrate sensors\n";
}
Thread.sleep(2000);
publishProgress(80);
//Finish
loading.setMessage("Finishing...");
Thread.sleep(1000);
publishProgress(90);
//Clear
loading.setMessage("Clearing some stuff...");
Thread.sleep(1000);
publishProgress(100);
return true;
} catch (Exception e){
return false;
}
}
protected void onProgressUpdate(Integer... values) {
super.onProgressUpdate(values[0]);
dialog.setProgress(values[0]);
}
}
但是当我启动活动时，应用会停止:(
这是输出：
03-06 12:32:35.902 10648-10648/com.jules_citronic.racecarcontrol E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.jules_citronic.racecarcontrol, PID: 10648
Theme: themes:{default=overlay:theme.lonecm12.kikkosart.com.lonecm12, iconPack:theme.lonecm12.kikkosart.com.lonecm12, fontPkg:theme.lonecm12.kikkosart.com.lonecm12, com.android.systemui=overlay:theme.lonecm12.kikkosart.com.lonecm12, com.android.systemui.navbar=overlay:theme.lonecm12.kikkosart.com.lonecm12}
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.jules_citronic.racecarcontrol/com.jules_citronic.racecarcontrol.control}: android.view.WindowManager$BadTokenException: Unable to add window -- token null is not for an application
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2450)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2520)
at android.app.ActivityThread.-wrap11(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1363)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5466)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
Caused by: android.view.WindowManager$BadTokenException: Unable to add window -- token null is not for an application
at android.view.ViewRootImpl.setView(ViewRootImpl.java:571)
at android.view.WindowManagerGlobal.addView(WindowManagerGlobal.java:310)
at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:86)
at android.app.Dialog.show(Dialog.java:319)
at com.jules_citronic.racecarcontrol.control$ProgressTask.onPreExecute(control.java:109)
at android.os.AsyncTask.executeOnExecutor(AsyncTask.java:604)
at android.os.AsyncTask.execute(AsyncTask.java:551)
at com.jules_citronic.racecarcontrol.control.onCreate(control.java:84)
at android.app.Activity.performCreate(Activity.java:6251)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1108)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2403)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2520)
at android.app.ActivityThread.-wrap11(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1363)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5466)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
我对Threads和其他东西不是很好，所以我希望有人可以帮助我。
编辑： 我将getBaseContext更改为context并放置“context = control.this”。顺便说一句，control是我的活动/类的名称。现在它启动了活动，但从未显示ProgressDialog并且未连接到蓝牙。它给了我一个“错误”的祝酒词。
编辑： 例外导出：
03-06 13:09:04.858 15370-15535/com.jules_citronic.racecarcontrol E/MYAPP: exception
java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare()
at android.os.Handler.<init>(Handler.java:200)
at android.os.Handler.<init>(Handler.java:114)
at android.widget.Toast$TN.<init>(Toast.java:347)
at android.widget.Toast.<init>(Toast.java:103)
at android.widget.Toast.makeText(Toast.java:261)
at com.jules_citronic.racecarcontrol.control.ErrorMessage(control.java:301)
at com.jules_citronic.racecarcontrol.control$ProgressTask.doInBackground(control.java:135)
at com.jules_citronic.racecarcontrol.control$ProgressTask.doInBackground(control.java:90)
at android.os.AsyncTask$2.call(AsyncTask.java:295)
at java.util.concurrent.FutureTask.run(FutureTask.java:237)
at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:234)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1113)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:588)
at java.lang.Thread.run(Thread.java:818)
编辑： 有效 ：）。这是最后一堂课：
private class ProgressTask extends AsyncTask<String, Integer, Boolean> {
private ProgressDialog dialog;
private Context context;
public ProgressTask(Context context) {
this.context = context;
//dialog = new ProgressDialog(getBaseContext());
}
/** progress dialog to show user that the backup is processing. */
/** application context. */
protected void onPreExecute() {
dialog = new ProgressDialog(context);
dialog.setTitle("Loading connection...");
dialog.setMessage("Loading...");
dialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
dialog.setMax(100);
dialog.setProgress(0);
dialog.show();
}
@Override
protected void onPostExecute(final Boolean success) {
if (dialog.isShowing()) {
dialog.dismiss();
}
if (success) {
Toast.makeText(context, "OK", Toast.LENGTH_LONG).show();
} else {
Toast.makeText(context, "Error", Toast.LENGTH_LONG).show();
}
}
protected Boolean doInBackground(final String... args) {
try {
Looper.prepare();
} catch (Exception ex) {
Log.e("MYAPP", "Exception in looper " + ex.getMessage());
}
try{
//Get device ID
publishProgress(0);
try {
getDeviceId();
} catch (Exception ex) {
ErrorMessage("Couldn't get device ID");
ErrorAlert += "Error 101: Couldn't get device ID\n";
}
Thread.sleep(2000);
publishProgress(20);
//Open connection
try {
openConnection();
} catch (IOException ex) {
ErrorMessage("Couldn't open connection");
ErrorAlert += "Error 102: Couldn't open connection\n";
}
Thread.sleep(2000);
publishProgress(40);
//Testing connection
if (!mmSocket.isConnected()) {
ErrorMessage("Test failed!");
ErrorAlert += "Error 103: Test failed!\n";
}
Thread.sleep(2000);
publishProgress(60);
//Calibrate sensors
try {
sendCommand("c");
} catch (IOException ex) {
ErrorMessage("Couldn't calibrate sensors");
ErrorAlert += "Error 104: Couldn't calibrate sensors\n";
}
Thread.sleep(2000);
publishProgress(80);
//Finish
Thread.sleep(1000);
publishProgress(90);
//Clear
Thread.sleep(1000);
publishProgress(100);
return true;
} catch (Exception e){
Log.e("MYAPP", "exception", e);
return false;
}
}
protected void onProgressUpdate(Integer... values) {
super.onProgressUpdate(values[0]);
dialog.setProgress(values[0]);
if (values[0] == 0){
dialog.setMessage("Getting device ID...");
}
if (values[0] == 20){
dialog.setMessage("Opening connection...");
}
if (values[0] == 40){
dialog.setMessage("Testing connection...");
}
if (values[0] == 60){
dialog.setMessage("Calibrating sensors...");
}
if (values[0] == 80){
dialog.setMessage("Finishing...");
}
if (values[0] == 90){
dialog.setMessage("Clearing some stuff...");
}
}
}
答案 0 :(得分：1)
由于AsyncTask不从Context继承，因此无法访问当前上下文。
您必须将当前上下文作为参数传递给构造函数并将其设置在那里。
private Context context;
public ProgressTask(Context context) {
this.context = context;
}
然后从new ProgressTask(context).execute();
答案 1 :(得分：0)
更改AsyncTask的构造函数和onPreExecute()方法，如下所示：
public ProgressTask(Context c) {
//dialog = new ProgressDialog(getBaseContext());
context = c;
}
/** progress dialog to show user that the backup is processing. */
/** application context. */
private Context context;
protected void onPreExecute() {
dialog = new ProgressDialog(this.context);
dialog.setTitle("Loading connection...");
dialog.setMessage("Loading...");
dialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
dialog.setMax(100);
dialog.setProgress(0);
dialog.show();
}
然后，尝试在您的活动中创建AsyncTask实例：
ProgressTask task = new ProgressTask(YourActivity.this);
task.execute();
答案 2 :(得分：0)
发布的异常确实发生，因为您的上下文是基本上下文而不是活动。但是，我认为整个设置并不正确。
长时间运行任务的主要问题是，如果由于某种原因重新创建活动，它们可能会比活动更长（最常见的是更改设备方向）。在这种情况下，您最终可能会调用已经消失的活动方法，这将导致异常和意外行为。
我之前离开了another answer，其中概述了如何处理此问题。通常，您可以创建一个处理后台工作的加载器，并发送回表示已加载数据或当前状态的对象。加载器框架可以自动附加和分离到活动，因此您始终可以使用它的活动实例并避免出现问题。
答案 3 :(得分：0)
添加
try {
Looper.prepare();
} catch (Exception ex) {
Log.e(tag, "Exception in looper " + ex.getMessage());
}
doInBackground方法中的这些行。这些行应该在doInBackground方法的开头。我遇到了同样的例外，然后我尝试了这些行。
或
从onPreExecute方法中删除这些行并在构造函数中声明。
dialog = new ProgressDialog(getBaseContext());
dialog.setTitle("Loading connection...");
dialog.setMessage("Loading...");
dialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
dialog.setMax(100);
dialog.setProgress(0);
在onPreExecute方法中，只使用dialog.show()方法。
希望它能帮到你。
有关详细信息，请参阅this答案