请教退出与返回问题，谢谢
我做了个程序，在主界面设置6个按钮，为什么在主界面点击某一按钮进入一个二级界面时，点击二级界面中的“返回”按钮，并不是返回主界面，而是直接退出整个程序？
程序代码：package st.st.st;
//主界面
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.view.KeyEvent;
import android.view.View;
import android.view.Window;
import android.widget.ImageButton;
import android.widget.Toast;
public class St1Activity extends Activity {
// 定义一个变量，来标识是否退出
private static boolean isExit = false;
Handler mHandler = new Handler() {
@Override
public void handleMessage(Message msg) {
super.handleMessage(msg);
isExit = false;
}
};
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
initButton();
}
@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
if (keyCode == KeyEvent.KEYCODE_BACK) {
exit();
return false;
}
return super.onKeyDown(keyCode, event);
}
private void exit() {
if (!isExit) {
isExit = true;
Toast.makeText(getApplicationContext(), "再按一次退出程序",
Toast.LENGTH_SHORT).show();
// 利用handler延迟发送更改状态信息
mHandler.sendEmptyMessageDelayed(0, 2000);
} else {
finish();
System.exit(0);
}
}
private void initButton() {
// TODO Auto-generated method stub
ImageButton btn1=(ImageButton)findViewById(R.id.imageButton1);
ImageButton btn2=(ImageButton)findViewById(R.id.imageButton2);
ImageButton btn3=(ImageButton)findViewById(R.id.imageButton3);
ImageButton btn4=(ImageButton)findViewById(R.id.imageButton4);
ImageButton btn5=(ImageButton)findViewById(R.id.imageButton5);
ImageButton btn6=(ImageButton)findViewById(R.id.imageButton6);
//肥胖测试按钮
btn1.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
// TODO Auto-generated method stub
Intent intent = new Intent();
//设置Intent对象要启动的Activity
intent.setClass(St1Activity.this, St2.class);
//通过Intent对象启动另外一个Activity
startActivity(intent);
St1Activity.this.finish();
}
});
//体重记录按钮
btn2.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
// TODO Auto-generated method stub
Intent intent = new Intent();
//设置Intent对象要启动的Activity
intent.setClass(St1Activity.this, St3.class);
//通过Intent对象启动另外一个Activity
startActivity(intent);
St1Activity.this.finish();
}
});
//饮食记录按钮
btn3.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
// TODO Auto-generated method stub
Intent intent = new Intent();
//设置Intent对象要启动的Activity
intent.setClass(St1Activity.this, St4.class);
//通过Intent对象启动另外一个Activity
startActivity(intent);
St1Activity.this.finish();
}
});
//运动记录按钮
btn4.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
// TODO Auto-generated method stub
Intent intent = new Intent();
//设置Intent对象要启动的Activity
intent.setClass(St1Activity.this, St5.class);
//通过Intent对象启动另外一个Activity
startActivity(intent);
St1Activity.this.finish();
}
});
//加油提醒按钮
btn5.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
// TODO Auto-generated method stub
Intent intent = new Intent();
//设置Intent对象要启动的Activity
intent.setClass(St1Activity.this, St6.class);
//通过Intent对象启动另外一个Activity
startActivity(intent);
St1Activity.this.finish();
}
});
//退出按钮
btn6.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
// TODO Auto-generated method stub
finish();
System.exit(0);
}
});
}
}程序代码：package st.st.st;
//二级界面
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.text.Editable;
import android.text.TextWatcher;
import android.view.KeyEvent;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.RadioButton;
import android.widget.RadioGroup;
import android.widget.Toast;
public class St2 extends Activity {
//肥胖测试
public RadioGroup group;
public RadioButton man,woman;
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.a);
Button btn1=(Button)findViewById(R.id.button1);//返回主界面按钮
Button btn2=(Button)findViewById(R.id.button2);//计算按钮
//返回主界面按钮
btn1.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
// TODO Auto-generated method stub
// Intent intent = new Intent();
//设置Intent对象要启动的Activity
// intent.setClass(St2.this,St1Activity.class);
//通过Intent对象启动另外一个Activity
// startActivity(intent);
St2.this.finish();
}
});
//计算按钮事件
btn2.setOnClickListener(new Button.OnClickListener() {
public void onClick(View v) {
// TODO Auto-generated method stub
//取得输入的身高
EditText height=(EditText)findViewById(R.id.height);
float height1=0;
if(!height.getText().toString().equals("")){
if(!height.getText().toString().substring(0,1).equals(".")){
height1=Float.parseFloat(height.getText().toString());
}
}
/*取得选择的性别*/
String sex="";
group=(RadioGroup)findViewById(R.id.radioGroup);
man=(RadioButton)findViewById(R.id.radio0);
woman=(RadioButton)findViewById(R.id.radio1);
if(man.isChecked()){
woman.setChecked(false);
sex="M";
}
else{
woman.setChecked(true);
sex="F";
}
//判断身高是否为空
if(height1<100.0||height1>200.0||height.equals(null)){
height.requestFocus();
height.setError("取值范围100.0~200.0");
}
else if(height1>=100.0||height1>=200.0){
Intent intent=new Intent();
intent.setClass(St2.this, St2_1.class);
Bundle bundle=new Bundle();
bundle.putDouble("height", height1);
bundle.putString("sex", sex);
/*将Bundle对象assign给Intent*/
intent.putExtras(bundle);
/*调用St2_1*/
startActivity(intent);
}
}
});
}
}
