Activity中 findViewById 获取控件对象正确的代码位置

来源：互联网发布：心蓝软件编辑：程序博客网时间：2024/05/02 05:12

package com.xiuye.adnroid;import android.app.Activity;import android.content.Intent;import android.os.Bundle;import android.view.View;import android.view.View.OnClickListener;import android.view.Window;import android.widget.Button;import android.widget.Toast;public class SecondActivity extends Activity {@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);requestWindowFeature(Window.FEATURE_NO_TITLE);setContentView(R.layout.second_layout);//1Button button3 = (Button) findViewById(R.id.button3);//2final Intent intent = getIntent();button3.setOnClickListener(new OnClickListener() {@Overridepublic void onClick(View v) {String data = "接收到传递的信息是："+intent.getStringExtra("extra_data");Toast.makeText(SecondActivity.this, data, Toast.LENGTH_LONG).show();}});}}

setContentView必须在findViewById的前面，否则要报错，控件对象引用取不到对象报空指针异常NullPointerException

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