关于activity的活动周期以及intent

1.  关以activity 的活动周期

    

package com.bwf.a6_actlife;

import android.os.Bundle;
import android.app.Activity;
import android.content.res.Configuration;
import android.util.Log;
import android.view.Menu;
import android.widget.Toast;
/**
 * Activity的生命周期方法的调用规则
 *         第一次启动:onCreate-->onStart-->onResume
 *         按HOME键:onPuase-->onStop
 *         点击图标启动:onRestart-->onStart-->onResume
 *         按BACK键:onPause-->onStop-->onDestroy此时Activity对象已经被销毁，生命周期就结束
 *         转屏时:onPause-->onStop-->onDestroy销毁上一个Activity对象，
 *              onCreate-->onStart-->onResume重新创建了一个Activity对象
 *         onSaveInstanceState在Activity进行异常注销的时候调用比如转屏、切换语言、内存吃紧时，用来保存数据
 *             调用时机是onPause-->onSaveInstanceState-->onStop
 *         onRestoreInstanceState也是在上一次异常注销后需要恢复时调用，用来恢复数据
 *             调用时机onStrat-->onRestoreInstanceState-->onResume
 * */
public class MainActivity extends Activity {
    final String TAG = "fanhy";
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        
        myLog("... onCreate ...");
        if(savedInstanceState != null){
            myLog("。。。"+savedInstanceState.getString("my_data"));
        } else{
            myLog("。。。null");
        }
    }
    
    @Override
    protected void onRestoreInstanceState(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onRestoreInstanceState(savedInstanceState);
        
        if(savedInstanceState != null){
            myLog("onRestoreInstanceState..."+savedInstanceState.getString("my_data"));
        }else{
            myLog("onRestoreInstanceState...没有要恢复的数据");
        }
    }

    /**
     * 如果在AndroidManifest.xml中设置了android:configChanges属性则会调用onSaveInstanceState
     * 但不会调用onRestoreInstanceState
     * */
    @Override
    protected void onSaveInstanceState(Bundle outState) {
        // TODO Auto-generated method stub
        super.onSaveInstanceState(outState);
        myLog(".... onSaveInstanceState ...");
        outState.putString("my_data", "保存一下");
    }
    
    @Override
    public void onConfigurationChanged(Configuration newConfig) {
        // TODO Auto-generated method stub
        super.onConfigurationChanged(newConfig);
        
        myLog("...onConfigurationChanged,要更新的操作就放到此方法中实现...方向："
                +newConfig.orientation+"，语言："+newConfig.locale);
        
        Toast.makeText(getApplicationContext(), "执行onConfigurationChanged", 
                Toast.LENGTH_LONG).show();
    }
    
    @Override
    protected void onStart() {
        // TODO Auto-generated method stub
        super.onStart();
        myLog("... onStart ...");
    }

    @Override
    protected void onRestart() {
        // TODO Auto-generated method stub
        super.onRestart();
        myLog("... onRestart ...");
    }

    @Override
    protected void onResume() {
        // TODO Auto-generated method stub
        super.onResume();
        myLog("... onResume ...");
    }

    @Override
    protected void onPause() {
        // TODO Auto-generated method stub
        super.onPause();
        myLog("... onPause ...");
    }

    @Override
    protected void onStop() {
        // TODO Auto-generated method stub
        super.onStop();
        myLog("... onStop ...");
    }

    @Override
    protected void onDestroy() {
        // TODO Auto-generated method stub
        super.onDestroy();
        myLog("... onDestroy ...");
    }

    public void myLog(String s){
        Log.d(TAG, s);
    }
}

2. 关于intent意图

2.1 主页Java代码

package com.bwf.a6_switchact;

import android.os.Bundle;
import android.app.Activity;
import android.content.Intent;
import android.view.Menu;
import android.view.View;
import android.widget.EditText;

public class MainActivity extends Activity {
    EditText edt_1,edt_2;
    
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        
        edt_1 = (EditText) findViewById(R.id.edt_num_1);
        edt_2 = (EditText) findViewById(R.id.edt_num_2);
        
    }
    
    public void mainClick(View v){
        switch (v.getId()) {
        case R.id.btn_switch:
            // 跳转的操作在此分支实现
            // 创建Intent对象
            Intent intent = new Intent();
            // 指定跳转的两个页面
            // 参数1 当前页面
            // 参数2 目标页面
            intent.setClass(MainActivity.this, SecondActivity.class);
            
            // 获取两个EditText中的值
            String str1 = edt_1.getText()+"";
            String str2 = edt_2.getText()+"";
            
            // 将数据直接放入Intent对象
            //intent.putExtra("num1", str1);
            //intent.putExtra("num2", str2);
            
            // 将数据封装到Bundle对象中
            Bundle bundle = new Bundle();
            // 给bundle对象绑定一些值
            bundle.putString("num1", str1);
            bundle.putString("num2", str2);
            // 把bundle绑定到Intent对象
            intent.putExtras(bundle);
            
            // 跳转的方法startActivity
            startActivity(intent);
            
            // 上述步骤合在一起
            //startActivity(new Intent(MainActivity.this, SecondActivity.class));
            //finish();
            break;

        default:
            break;
        }
    }
}

2.2 分页Java代码

package com.bwf.a6_switchact;

import android.os.Bundle;
import android.app.Activity;
import android.content.Intent;
import android.view.Menu;
import android.view.View;
import android.widget.TextView;

public class SecondActivity extends Activity {
    TextView tv_result;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_second);
        
        tv_result = (TextView) findViewById(R.id.tv_result);    
    }

    public void secondClick(View v){
        switch (v.getId()) {
        case R.id.btn_caculate:
            // 获取到MainActivity传递过来的Intent对象
            Intent intent = getIntent();
            // 从该Intent对象中取出数据
            //int num1 = Integer.parseInt(intent.getStringExtra("num1"));
            //int num2 = Integer.parseInt(intent.getStringExtra("num2"));
            
            // 通过Intent对象把bundle取出
            Bundle b = intent.getExtras();
            int num1 = Integer.parseInt(b.getString("num1"));
            int num2 = Integer.parseInt(b.getString("num2"));
            
            // 加法运算
            int num = num1 + num2;
            // 把结果转成需要的字符串
            String str = num1 + "+" + num2 + "=" + num;
            // 把该字符串设置到TextView上
            tv_result.setText(str);
            
            break;

        default:
            break;
        }
    }
}