我正在尝试将文本从多个文本框保存到单个文件中，并将其自身排列在表格中
例如：
学生：....
分类：...
标记：......
这应该保存为：
Student Class Marks .... .... .... .... .... ....
每次保存时，都应为新学生创建一个新行....
这可以作为文本文件吗？ 如果没有，我还能做到这一点吗？
此外，活动应显示此表....如果可能
我得到的代码是：
public class Save extends Activity implements SwipeInterface, OnFocusChangeListener {
Double marks = 0.0;
EditText et1 = (EditText) findViewById(R.id.roll_no);
EditText et2 = (EditText) findViewById(R.id.name);
EditText et3 = (EditText) findViewById(R.id.grade);
EditText et4 = (EditText) findViewById(R.id.subject);
EditText et5 = (EditText) findViewById(R.id.marks);
EditText et6 = (EditText) findViewById(R.id.filename);
....
ActivitySwipeDetector swipe = new ActivitySwipeDetector(this, this);
RelativeLayout swipe_layout = (RelativeLayout) findViewById(R.id.Save_port);
swipe_layout.setOnTouchListener(swipe);
Intent receiveIntent = this.getIntent();
Double e3 = receiveIntent.getDoubleExtra("DoubleValue_e3", 0.00);
marks = e3;
EditText ebar = (EditText) findViewById(R.id.marks);
ebar.setText(marks.toString());
et3.setOnFocusChangeListener((OnFocusChangeListener)this);
try{
File dir = new File("/mnt/sdcard/Teacher's Aid/");
if (!dir.exists()) {
dir.mkdir();
}
}catch (Exception e) {
// TODO: handle exception
e.printStackTrace();
}
}
....
public void butt_save(View view)
{
try {
String row = et1.getText().toString() + "," + et2.getText().toString() + "," + et3.getText().toString() + "," + et4.getText().toString() + "," + et5.getText().toString() + "\n";
File myFile = new File("/mnt/sdcard/Teacher's Aid/" + et6.getText().toString() + ".csv");
if (!myFile.exists()) {
myFile.createNewFile();
FileOutputStream fOut = new FileOutputStream(myFile.getAbsoluteFile(),true);
OutputStreamWriter myOutWriter = new OutputStreamWriter(fOut);
//Write the header : in your case it is : Student class Marsk (only one time)
myOutWriter
.write("Roll no,Name,Grade,Subject,Marks"+"\n");
myOutWriter.close();
}
FileOutputStream fOut = new FileOutputStream(myFile.getAbsoluteFile(),true);
OutputStreamWriter myOutWriter = new OutputStreamWriter(fOut);
//write to CSV
myOutWriter.write(row);
myOutWriter.close();
Toast.makeText(getApplication(), "Sucessful",Toast.LENGTH_LONG).show();
} catch (Exception e) {
e.printStackTrace();
}
}
@Override
public void onFocusChange(View v, boolean hasFocus) {
if(!hasFocus)
{
et6.setText("Class " + et3.getText().toString());
}
}}
然而，这甚至没有打开......当我从主要活动转到此时，你的应用程序崩溃了.... LogCat显示......
02-20 05:53:38.581: E/AndroidRuntime(1664): FATAL EXCEPTION: main
02-20 05:53:38.581: E/AndroidRuntime(1664): Process: com.Candy.teacher, PID: 1664
02-20 05:53:38.581: E/AndroidRuntime(1664): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.Candy.teacher/com.Candy.teacher.Save}: java.lang.NullPointerException
02-20 05:53:38.581: E/AndroidRuntime(1664): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2102)
02-20 05:53:38.581: E/AndroidRuntime(1664): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2226)
02-20 05:53:38.581: E/AndroidRuntime(1664): at android.app.ActivityThread.access$700(ActivityThread.java:135)
02-20 05:53:38.581: E/AndroidRuntime(1664): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1397)
02-20 05:53:38.581: E/AndroidRuntime(1664): at android.os.Handler.dispatchMessage(Handler.java:102)
02-20 05:53:38.581: E/AndroidRuntime(1664): at android.os.Looper.loop(Looper.java:137)
02-20 05:53:38.581: E/AndroidRuntime(1664): at android.app.ActivityThread.main(ActivityThread.java:4998)
02-20 05:53:38.581: E/AndroidRuntime(1664): at java.lang.reflect.Method.invokeNative(Native Method)
02-20 05:53:38.581: E/AndroidRuntime(1664): at java.lang.reflect.Method.invoke(Method.java:515)
02-20 05:53:38.581: E/AndroidRuntime(1664): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:777)
02-20 05:53:38.581: E/AndroidRuntime(1664): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:593)
02-20 05:53:38.581: E/AndroidRuntime(1664): at dalvik.system.NativeStart.main(Native Method)
02-20 05:53:38.581: E/AndroidRuntime(1664): Caused by: java.lang.NullPointerException
02-20 05:53:38.581: E/AndroidRuntime(1664): at android.app.Activity.findViewById(Activity.java:1883)
02-20 05:53:38.581: E/AndroidRuntime(1664): at com.Candy.teacher.Save.<init>(Save.java:15)
02-20 05:53:38.581: E/AndroidRuntime(1664): at java.lang.Class.newInstanceImpl(Native Method)
02-20 05:53:38.581: E/AndroidRuntime(1664): at java.lang.Class.newInstance(Class.java:1208)
02-20 05:53:38.581: E/AndroidRuntime(1664): at android.app.Instrumentation.newActivity(Instrumentation.java:1061)
02-20 05:53:38.581: E/AndroidRuntime(1664): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2093)
02-20 05:53:38.581: E/AndroidRuntime(1664): ... 11 more
02-20 05:53:50.241: I/Process(1664): Sending signal. PID: 1664 SIG: 9
答案 0 :(得分：2)
首先包括权限：
android.permission.WRITE_EXTERNAL_STORAGE
您必须使用FileOutputStream：
File externalStorageDir = Environment.getExternalStorageDirectory();
File myFile = new File(externalStorageDir , "mysdfile.txt");
if(myFile.exists())
{
try
{
FileOutputStream fOut = new FileOutputStream(myFile);
OutputStreamWriter myOutWriter = new OutputStreamWriter(fOut);
myOutWriter.append(string);
myOutWriter.close();
fOut.close();
} catch(Exception e)
{
}
}
else
{
myFile.createNewFile();
}
在将字符串写入文件之前，请附加字符串，以便存储详细信息：
StringBuffer string = new StringBuffer();
那么你可以简单地使用：
string.append(editText1.getText());
string.append(" ; ");
string.append(editText2.getText());
string.append(" ; ");
string.append(editText3.getText());
答案 1 :(得分：1)
只需使用标题创建制表符分隔文件，然后将新值添加到此文件的末尾。看看http://docs.oracle.com/javase/tutorial/essential/io/
答案 2 :(得分：1)
如果您想在SD卡中存储.csv文件，请尝试下面的代码
try{
File dir = new File("/mnt/sdcard/MyApp/");
if (!dir.exists()) {
dir.mkdir();
System.out.println("Directory created");
}
//ceate .csv file with header
myFile = new File("/mnt/sdcard/MyApp/Student.csv");
if (!myFile.exists()) {
myFile.createNewFile();
System.out.println("File created");
}
fOut = new FileOutputStream(myFile.getAbsoluteFile(),true);
myOutWriter = new OutputStreamWriter(fOut);
//Write the header : in your case it is : Student class Marsk (only one time)
myOutWriter
.write("Student,class,Marks"+"\n");
myOutWriter.flush();
}catch (Exception e) {
// TODO: handle exception
e.printStackTrace();
}
如果要编写新行：
try {
String row = studentname + "," + studentclass + "," + studentmarks + "\n";
myFile = new File("/mnt/sdcard/MyApp/Student.csv");
if (!myFile.exists()) {
myFile.createNewFile();
}
fOut = new FileOutputStream(myFile.getAbsoluteFile(),true);
myOutWriter = new OutputStreamWriter(fOut);
//write to CSV
myOutWriter.write(row);
myOutWriter.flush();
System.out.println("write to student csv .....");
} catch (Exception e) {
e.printStackTrace();
}
现在检查你的sdcard / MyApp / Student.csv文件