DrawerLayout使用问题 哪里有问题 点击图片后停止运行并报错

Question

错误
java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v4.widget.DrawerLayout.openDrawer(android.view.View)' on a null object reference
at com.cy.mynj.com.cy.mynj.activities.MainActivity.onClick(MainActivity.java:57)
at android.view.View.performClick(View.java:4848)
at android.view.View$PerformClick.run(View.java:20300)
at android.os.Handler.handleCallback(Handler.java:815)
at android.os.Handler.dispatchMessage(Handler.java:104)
at android.os.Looper.loop(Looper.java:194)
at android.app.ActivityThread.main(ActivityThread.java:5682)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:963)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:758)

public class MainActivity extends AppCompatActivity implements View.OnClickListener{
//左边栏
private List mList = new ArrayList();
private ListView mListView;
DrawerLayout mDrawerLayout;
//
private ImageView iv_left;

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    initData();
    initViews();
}

private void initData() {
    mList.add(new ContentModel(R.drawable.weather_icons, "天气", 1));
    mList.add(new ContentModel(R.drawable.scenic_spot_icon, "本地美景", 2));
    mList.add(new ContentModel(R.drawable.bus_icon, "交通", 3));
    mList.add(new ContentModel(R.drawable.security_icon, "社保", 4));
    mList.add(new ContentModel(R.drawable.insurance_icon, "医疗", 5));
    mList.add(new ContentModel(R.drawable.ciziten_card_icon, "市民卡", 6));
    mList.add(new ContentModel(R.drawable.employ_icon, "招聘", 7));
    mList.add(new ContentModel(R.drawable.news_icon, "新闻", 8));
}
private void initViews(){
    mListView = (ListView) findViewById(R.id.left_listview);
    ContentAdapter adapter = new ContentAdapter(this,mList);
    mListView.setAdapter(adapter);

    iv_left = (ImageView)findViewById(R.id.leftmenu);
    iv_left.setOnClickListener(this);

}

@Override
public void onClick(View view) {
    switch (view.getId()){
        case R.id.leftmenu:
            **mDrawerLayout.openDrawer(Gravity.LEFT);**
            break;
        default:
            break;
    }
}

}

Answer 1

*mDrawerLayout.openDrawer(Gravity.LEFT);

这个东西没有初始化