带有方法的Android服务错误

Question

我正在尝试调用一个名为GetText(); 的方法，该方法将布局上的TextView 从MainActivity 更改为。我正在使用服务类调用此方法，每次调用此方法时，我的程序都会完全崩溃并出现FATAL EXCEPTION 错误。

//主活动

package com.example.modulefour;

import android.content.Intent;
import android.os.Bundle;
import android.support.v7.app.ActionBarActivity;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

public class MainActivity extends ActionBarActivity {

    Button BtnStart, BtnStop;
    EditText Edt;
    TextView one;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        BtnStart = (Button)findViewById(R.id.button1);
        BtnStop = (Button) findViewById(R.id.button2);
        Edt = (EditText) findViewById(R.id.editText1);
        one = (TextView) findViewById(R.id.textView1);

    }

    public void GetText()
    {
        String Text = this.Edt.getText().toString();
        this.one.setText(Text);
    }
    public void StartService(View v){
        //start Service 
        startService(new Intent(getBaseContext(), ServiceAdapter.class));
    }

    public void StopService(View v){
        //stop service
        GetText();
    }

    @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;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();
        if (id == R.id.action_settings) {
            return true;
        }
        return super.onOptionsItemSelected(item);
    }
}

//服务适配器

package com.example.modulefour;

import java.io.BufferedWriter;
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;

import android.app.Service;
import android.content.Intent;
import android.os.IBinder;
import android.widget.Toast;

public class ServiceAdapter extends Service {

    MainActivity main;
    FileWriter fw;
    BufferedWriter bw;


    @Override
    public IBinder onBind(Intent arg0) {
        // TODO Auto-generated method stub
        return null;
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId)
    {
        this.main.GetText();
        Toast.makeText(this, "Service Started", Toast.LENGTH_LONG).show();

        //write EditText to text file

        return START_STICKY;
    }



    @Override
    public void onDestroy()
    {
        super.onDestroy();
        Toast.makeText(this, "Service Stopped", Toast.LENGTH_LONG).show();
    }


}

Answer 1

你的服务类中的main 没有设置在任何地方，所以this.main.GetText() 你会得到一个NullPointerException。

对于您想要做的事情，请查看一般情况下如何在 Activity 和 Service 之间进行通信。主要是，您要么必须绑定服务，要么使用某种广播方法。