问题描述
我新建了一个hellowworld不支持啊
package com.xiaogu.ui;import android.app.Activity;import android.os.Bundle;import android.support.design.widget.Snackbar;import android.view.View;import android.widget.Button;import com.xiaogu.R;import butterknife.BindView;import butterknife.ButterKnife;public class MainActivity extends Activity { @BindView(R.id.btn) Button btn; @Override protected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);ButterKnife.bind(this);btn.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View view) {Snackbar.make(findViewById(R.id.btn), 'SnackbarClicked', Snackbar.LENGTH_SHORT).show(); }}); } }
10-21 14:58:30.440 18007-18007/com.xiaogu E/AndroidRuntime: FATAL EXCEPTION: mainProcess: com.xiaogu, PID: 18007java.lang.RuntimeException: Unable to start activity ComponentInfo{com.xiaogu/com.xiaogu.ui.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method ’void android.widget.Button.setOnClickListener(android.view.View$OnClickListener)’ on a null object reference at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2416) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476) at android.app.ActivityThread.-wrap11(ActivityThread.java) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:148) at android.app.ActivityThread.main(ActivityThread.java:5417) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616) Caused by: java.lang.NullPointerException: Attempt to invoke virtual method ’void android.widget.Button.setOnClickListener(android.view.View$OnClickListener)’ on a null object reference at com.xiaogu.ui.MainActivity.onCreate(MainActivity.java:25) at android.app.Activity.performCreate(Activity.java:6251) at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1107) at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2369) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476) at android.app.ActivityThread.-wrap11(ActivityThread.java) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:148) at android.app.ActivityThread.main(ActivityThread.java:5417) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
问题解答
回答1：没问题的支持
