app-自學Android開發 在模擬器運行閃退

自學Android開發 在模擬器運行閃退

初學者自寫的程序 ，但是在模擬器下運行閃退！！該怎麼改呀？？

package com.example.work3;

import java.util.ArrayList;
import java.util.List;
import android.support.v7.app.ActionBarActivity;
import android.support.v7.app.ActionBar;
import android.support.v4.app.Fragment;
import android.annotation.SuppressLint;
import android.app.AlertDialog;
import android.app.TabActivity;
import android.content.DialogInterface;
import android.graphics.drawable.Drawable;
import android.os.Bundle;
import android.os.StrictMode;
import android.view.KeyEvent;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.Spinner;
import android.widget.TabHost;
import android.widget.TextView;
import android.os.Build;

public class MainActivity extends TabActivity {
private TabHost tabhost;
private ListView listview;
private ArrayAdapter arr_adapter;
private Spinner spinner;
private Listlist;
private ArrayAdapter adapter;
private EditText et1,et2;
private Button bt;
String name;
String value;
String style;
@SuppressLint("NewApi") @Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
et1=(EditText) findViewById(R.id.editText1);
et2=(EditText) findViewById(R.id.editText2);
bt=(Button) findViewById(R.id.button1);
setContentView(R.layout.activity_main);
tabhost=getTabHost();
tabhost.addTab(tabhost.newTabSpec("菜單一").setIndicator("首頁").setContent(R.id.tab1));
tabhost.addTab(tabhost.newTabSpec("菜單二").setIndicator("新增").setContent(R.id.tab2));
tabhost.addTab(tabhost.newTabSpec("菜單三").setIndicator("賬單").setContent(R.id.tab3));
//按鈕監聽 提取信息

    bt.setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View arg0) {
            // TODO Auto-generated method stub
             name = et1.getText().toString();
             value = et2.getText().toString();
            style = spinner.getSelectedItem().toString();
        }
    });
    listview = (ListView) findViewById(R.id.listview);
    //新建適配器
    String[]arr_data={"數據1","數據2","數據3","數據4","數據5"};
    //ArrayAdapter(上下文，當前ListView加載的每一個列表項所對應的布局文件，數據源)
    arr_adapter =new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1,arr_data);
    listview.setAdapter(arr_adapter);
    spinner=(Spinner) findViewById(R.id.spinner);
    //數據源
    String[]list = {"1.日常食品支出","2.人情世故支出","3.出差旅游支出","4.服飾鞋帽支出","5.生活用品支出","6.其他支出"};
    //新建適配器

    adapter=new ArrayAdapter<String>(this, android.R.layout.simple_spinner_item, list);
    //設置下拉樣式
    adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
    //加載適配器
    spinner.setAdapter(adapter);
}

//退出對話框
 @Override  
    public boolean onKeyDown(int keyCode, KeyEvent event)  
    {  
        if (keyCode == KeyEvent.KEYCODE_BACK )  
        {  
            // 創建退出對話框  
            AlertDialog isExit = new AlertDialog.Builder(this).create();  
            // 設置對話框標題  
            isExit.setTitle("系統提示");  
            // 設置對話框消息 

            isExit.setMessage("確定要退出嗎");  
            // 添加選擇按鈕並注冊監聽  
            isExit.setButton("確定", listener);  
            isExit.setButton2("取消", listener);  
            // 顯示對話框  
            isExit.show();  

        }  

        return false;  

    }  
    /**監聽對話框裡面的button點擊事件*/  
    DialogInterface.OnClickListener listener = new DialogInterface.OnClickListener()  
    {  
        public void onClick(DialogInterface dialog, int which)  
        {  
            switch (which)  
            {  
            case AlertDialog.BUTTON_POSITIVE:// "確認"按鈕退出程序  
                finish();  
                break;  
            case AlertDialog.BUTTON_NEGATIVE:// "取消"第二個按鈕取消對話框  
                break;  
            default:  
                break;  
            }  
        }  
    };    

}

最佳回答：

你以後應該把錯誤log也貼出來，這樣看可能會太累。不過幸好錯誤點很清晰：
et1=(EditText) findViewById(R.id.editText1);
et2=(EditText) findViewById(R.id.editText2);
bt=(Button) findViewById(R.id.button1);
setContentView(R.layout.activity_main);

你報的是空指針錯誤，et1、et2、bt都賦的是null，原因是你的布局文件還沒傳進去解析。應該改成這樣，setContentView要早於findviewby
setContentView(R.layout.activity_main);
et1=(EditText) findViewById(R.id.editText1);
et2=(EditText) findViewById(R.id.editText2);
bt=(Button) findViewById(R.id.button1);