请教大家一下，我想在onMenuOpened()方法里通过获取一个Item从而修改它的title 但总是抛出NullPointerException

Konvin_Zhi 2014-02-14 05:39:43

如题，我是一个新入Android阵型的小白，多谢各位大大了

menu=>main.xml

<menu xmlns:android="http://schemas.android.com/apk/res/android" >

    <item

         android:id="@+id/menu_prefs"

         android:title="@string/menu_prefs"

         android:icon="@android:drawable/ic_menu_preferences"></item>

    <item 

        android:id="@+id/server8"

        android:title="开始"></item>

    <item 

        android:id="@+id/OpenShowView"

        android:title="显示更新"/>

</menu>

MainActivity.java

package com.example.countinput;



import android.os.Binder;

import android.os.Bundle;

import android.preference.PreferenceManager;

import android.app.Activity;

import android.content.Intent;

import android.content.SharedPreferences;

import android.content.SharedPreferences.OnSharedPreferenceChangeListener;

import android.database.Cursor;

import android.database.sqlite.SQLiteDatabase;

import android.graphics.Color;

import android.text.Editable;

import android.text.TextWatcher;

import android.util.Log;

import android.view.Menu;

import android.view.MenuInflater;

import android.view.MenuItem;

import android.view.View;

import android.widget.EditText;

import android.widget.SimpleCursorAdapter;

import android.widget.SimpleCursorAdapter.ViewBinder;

import android.widget.TextView;



public class MainActivity extends Activity implements TextWatcher,OnSharedPreferenceChangeListener {



	private SharedPreferences prefs;

	private TextView text_count;

	private EditText input;

	private Count_Application ca;

	

	@Override

	public boolean onCreateOptionsMenu(Menu menu) {

		// TODO Auto-generated method stub

		MenuInflater Inflater = this.getMenuInflater();

		Inflater.inflate(R.menu.main, menu);

		return true;

	}



	@Override

	public boolean onOptionsItemSelected(MenuItem item) {

		// TODO Auto-generated method stub

		switch(item.getItemId()){

		case R.id.menu_prefs:

			this.startActivity(new Intent(this,PrefsActivity.class));

			break;

		case R.id.server8:

			if(ca.GetServer()){

				this.startService(new Intent(this,Update_Server.class));

			}else{

				this.stopService(new Intent(this,Update_Server.class));

			}

			break;

		case R.id.OpenShowView:

			this.startActivity(new Intent(this,ShowActivity.class).addFlags(Intent.FLAG_ACTIVITY_BROUGHT_TO_FRONT));

			break;

		}

		return true;

	}

	@Override

	public boolean onMenuOpened(int featureId, Menu menu) {

		// TODO Auto-generated method stub

		menu.findItem(R.id.server8);

		return super.onMenuOpened(featureId, menu);

	}

	@Override

	protected void onCreate(Bundle savedInstanceState) {

		super.onCreate(savedInstanceState);

		setContentView(R.layout.activity_main);

		text_count = (TextView)this.findViewById(R.id.counts);

		input = (EditText)this.findViewById(R.id.eidts);

		input.addTextChangedListener(this);

		prefs = PreferenceManager.getDefaultSharedPreferences(this);

		prefs.registerOnSharedPreferenceChangeListener(this);

		ca = (Count_Application)this.getApplication();

		//DBHelper dbs = new DBHelper(this);

		//SQLiteDatabase db = dbs.getReadableDatabase();

		//input.setText(prefs.getString("UserName", ""));

	}

;

	@Override

	public void afterTextChanged(Editable s) {

		// TODO Auto-generated method stub

		

		int text_lenght = 140 -s.length();

		//this.text_count.setText(String.valueOf(text_lenght));

		this.text_count.setTextColor(Color.GREEN);

		if(text_lenght<10){

			this.text_count.setTextColor(Color.YELLOW);

		}

		if(text_lenght<0){

			this.text_count.setTextColor(Color.RED);

		}

		

	}



	@Override

	public void beforeTextChanged(CharSequence s, int start, int count,

			int after) {

		// TODO Auto-generated method stub

		//input.setText(prefs.getString("UserName", ""));

		

	}



	@Override

	public void onTextChanged(CharSequence s, int start, int before, int count) {

		// TODO Auto-generated method stub

		

	}



	@Override

	public void onSharedPreferenceChanged(SharedPreferences arg0, String arg1) {

		// TODO Auto-generated method stub

		//input.setText(prefs.getString("UserName", ""));

		Count_Application apps = (Count_Application)this.getApplication();

		input.setText(apps.getCount());

	}

	

}