一段时间以来, Eric Nordvik一直在帮助我解决这个问题,这对他来说非常重要。
这个问题已经演变成一个 AsyncTask 问题,所以我想我会把它移到这里。单击打印按钮 (btnPrintTardy) 时,我将启动 AsyncTask 以通过 FileWriter 将编辑文本字段 (editText1) 中的任何内容作为 .text 保存到 SD 卡。
到目前为止,这是我的 AsyncTask,名为“FileWriterTask”
package com.android.upgrayeddapps.latepass;
import java.io.File;
import java.io.FileOutputStream;
import java.io.OutputStreamWriter;
import android.content.Context;
import android.os.AsyncTask;
import android.view.View;
import android.widget.Toast;
public class FileWriterTask extends AsyncTask<String, Void, Void> {
@Override
protected Void doInBackground(String... params) {
// write in data folder
try {
File myFile = new File("/sdcard/StudentLatePass.txt");
myFile.createNewFile();
FileOutputStream fOut = new FileOutputStream(myFile);
OutputStreamWriter myOutWriter =
new OutputStreamWriter(fOut);
myOutWriter.append(params[0]);
myOutWriter.close();
fOut.close();
Toast.makeText(getBaseContext(),
"Finished writing StudentLatePass.txt'",
Toast.LENGTH_SHORT).show();
} catch (Exception e) {
Toast.makeText(getBaseContext(), e.getMessage(),
Toast.LENGTH_SHORT).show();
}
finish();
return null;
}
private Context getBaseContext() {
// TODO Auto-generated method stub
return null;
}
private void finish() {
// TODO Auto-generated method stub
};
public void onClick(View v) {
// clear text box
finish();
}
}
在我的学生活动中,我用这段代码调用我的 FileWriterTask。
public void UpdateStudenttxtfile(View View)
{
EditText txtData = (EditText) findViewById(R.id.editText1);
FileWriterTask task = new FileWriterTask();
task.execute(txtData.getText().toString());
}
在我的 studentActivity 布局中,我将 Click 上的“打印按钮”设置为
android:onClick="UpdateStudenttxtfile"
现在,当我运行它时,我遇到了一些异常并且程序崩溃了。
I/dalvikvm(337): Jit: resizing JitTable from 512 to 1024
W/dalvikvm(337): threadid=9: thread exiting with uncaught exception (group=0x40015560)
E/AndroidRuntime(337): FATAL EXCEPTION: AsyncTask #1
E/AndroidRuntime(337): java.lang.RuntimeException: An error occured while executing doInBackground()
E/AndroidRuntime(337): at android.os.AsyncTask$3.done(AsyncTask.java:200)
E/AndroidRuntime(337): at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:274)
E/AndroidRuntime(337): at java.util.concurrent.FutureTask.setException(FutureTask.java:125)
E/AndroidRuntime(337): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:308)
E/AndroidRuntime(337): at java.util.concurrent.FutureTask.run(FutureTask.java:138)
E/AndroidRuntime(337): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1088)
E/AndroidRuntime(337): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:581)
E/AndroidRuntime(337): at java.lang.Thread.run(Thread.java:1019)
E/AndroidRuntime(337): Caused by: java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare()
E/AndroidRuntime(337): at android.os.Handler.<init>(Handler.java:121)
E/AndroidRuntime(337): at android.widget.Toast.<init>(Toast.java:68)
E/AndroidRuntime(337): at android.widget.Toast.makeText(Toast.java:231)
E/AndroidRuntime(337): at com.android.upgrayeddapps.latepass.FileWriterTask.doInBackground(FileWriterTask.java:29)
E/AndroidRuntime(337): at com.android.upgrayeddapps.latepass.FileWriterTask.doInBackground(FileWriterTask.java:1)
E/AndroidRuntime(337): at android.os.AsyncTask$2.call(AsyncTask.java:185)
E/AndroidRuntime(337): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:306)
E/AndroidRuntime(337): ... 4 more
D/dalvikvm(337): GC_CONCURRENT freed 1381K, 60% free 2709K/6727K, external 2011K/2137K, paused 7ms+8ms
I/Process(337): Sending signal. PID: 337 SIG: 9