此android代码导致我的应用崩溃

Question

I am new to android development using Java, and I came to how to save application data in SharedPreferences class ..

When trying to make this attempt, the app crashs ..

This android java code causes the app to crash when trying to save the data

package com.example.savedata;

import android.app.Activity;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.view.Menu;
import android.view.View;
import android.widget.TextView;

public class MainActivity extends Activity {
SharedPreferences sp;
@Override
protected void onCreate(Bundle savedInstanceState) {
    TextView tv;
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    sp = getSharedPreferences ("MYFILENAME",MODE_PRIVATE);
    tv = (TextView)findViewById(R.id.txtData);
    tv.setText(sp.getString("Data","0"));
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.main, menu);
    return true;
}
public void saveDate(View v){
    sp = getSharedPreferences("MYFILENAME", MODE_PRIVATE);
    TextView tv;
    SharedPreferences.Editor ed = sp.edit();
    tv = (TextView)findViewById(R.id.txtData);
    ed.putString("Data", (String) tv.getText());
    ed.commit();
}

}

Can anybody help me telling why does this code crash ?

Answer 1

you can try this,

instead of this:

ed.putString("Data", (String) tv.getText());

you can use:

ed.putString("Data", tv.getText().toString());