小编gna*_*gie的帖子

我正在尝试为我的应用程序实现抽屉导航,但我似乎无法启动它,我无法弄清楚为什么.它在setAdapter返回一个空指针异常,但我不明白,因为这是复制和过去几乎来自android和其他类似的教程.谁能告诉我我做错了什么？

主要活动

import android.app.Activity;
import android.os.Bundle;
import android.support.v4.widget.DrawerLayout;
import android.util.Log;
import android.view.Menu;
import android.widget.ArrayAdapter;
import android.widget.ListView;

public class MainActivity extends Activity {
    private String[] mContentTitles;
    private DrawerLayout mDrawerLayout;
    private ListView mDrawerList;
    private final String TAG = "MainActivity";


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        mContentTitles = getResources().getStringArray(R.array.contentTitles);
        mDrawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);
        mDrawerList = (ListView) findViewById(R.id.left_drawer);

        mDrawerList.setAdapter(new ArrayAdapter<String>(this, R.layout.drawer_list_item, mContentTitles));

    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it …