                        课程
                    
                        /移动开发
                        
                            /Android
                        
                        /Android攻城狮的第二门课（第1季）

请帮忙看一下为什么程序会崩溃

public class MainActivity extends AppCompatActivity {

private ListView listView;
private SimpleAdapter simpleAdapter;
private List<Map<String,Object>> datalist;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
listView=(ListView)findViewById(R.id.listView);
simpleAdapter=new SimpleAdapter(this,getData(),R.layout.item,new String[]{"pic","textview"},new int[]{R.id.pic,R.id.textView});
listView.setAdapter(simpleAdapter);
}
private List<Map<String,Object>> getData()
{
for(int i=0;i<10;i++) {
Map<String,Object> map=new HashMap<String,Object>();
map.put("pic", R.mipmap.ic_launcher);
map.put("textview", "text"+i);
datalist.add(map);
}
return datalist;
}
}

错误日志：

Process: com.example.myapplication, PID: 18831

java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.myapplication/com.example.myapplication.MainActivity}: java.lang.NullPointerException: Attempt to invoke interface method 'boolean java.util.List.add(java.lang.Object)' on a null object reference

at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2460)

at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2522)

at android.app.ActivityThread.access$800(ActivityThread.java:167)

at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1417)

at android.os.Handler.dispatchMessage(Handler.java:111)

at android.os.Looper.loop(Looper.java:179)

at android.app.ActivityThread.main(ActivityThread.java:5543)

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:955)

at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:750)

Caused by: java.lang.NullPointerException: Attempt to invoke interface method 'boolean java.util.List.add(java.lang.Object)' on a null object reference

at com.example.myapplication.MainActivity.getData(MainActivity.java:34)

at com.example.myapplication.MainActivity.onCreate(MainActivity.java:25)

at android.app.Activity.performCreate(Activity.java:5975)

at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1111)