Android 向手动输入的文件名添加扩展名

经过多次尝试后，我无法为文件设置用户输入名称，也无法在文件末尾自动添加扩展名。所以在我的例子中，我有一个简单的.txt文件，我试图使用onClickListener保存我的文件

通常它的工作原理如下：

public void onClick(View view) {                
            try {
                FileOutputStream fout =
                    openFileOutput("filename_here.txt" , MODE_WORLD_READABLE);

但是我想让用户在这里设置个人标题，所以我在活动中有：

        save.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            Message = maintext.getText().toString();
            try {
                FileOutputStream fout = openFileOutput(title.getText().toString()+".txt" , MODE_WORLD_READABLE); //look at the extension .txt
                OutputStreamWriter outsw = new OutputStreamWriter(fout);
                try {
                    outsw.write(Message);
                    outsw.flush();
                    outsw.close();
                    Toast.makeText(getBaseContext(), "Your file has been saved", Toast.LENGTH_LONG).show();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            } catch (FileNotFoundException e) {
                e.printStackTrace();
            }
        }
    });

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我不知道这种添加扩展的方式是否可行，但每当我按下保存按钮时，我的应用程序就会崩溃

我不得不手动将我的文件名放在onCreate void中，最后我添加了扩展名：

public class Save extends ActionBarActivity {

String FileName; //specify "FileName" as a string
EditText et;     //and "et" as an EditText

@Override
protected void onCreate(Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);
    this.setContentView(R.layout.activity_save);
    Button save = (Button) findViewById(R.id.SAVE);
    final EditText maintext = (EditText) findViewById(R.id.test); //my main text where i put personal things.        
    et = (EditText) findViewById(R.id.save_filename); //assign et (EditText) to an object (or vice-versa). In this case, EditText is found in my XML with id save_filename        


//Now setting onClickListener
save.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            try {
                //This line below make the trick
                //We set a string, FileName, to contain a name we input in our "et" EditText and an extension added with the + ".txt" (note that there are no space before and after the .txt)
                FileName = et.getText().toString() + ".txt"; 
                FileOutputStream fout = openFileOutput(FileName, Context.MODE_PRIVATE);
                OutputStreamWriter outsw = new OutputStreamWriter(fout);
                try {
                    outsw.write(String.valueOf(maintext));
                    outsw.flush();
                    outsw.close();
                    Toast.makeText(getBaseContext(), "File Saved Successfully", Toast.LENGTH_SHORT).show();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            } catch (FileNotFoundException e) {
                e.printStackTrace();
            }

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发布日志猫错误。