Android周学习Step By Step（8）--Intent之启动新的Activity

Intent的官方定义：An intent is an abstract description of an operation to be performed。一个Intent就是一次对将要执行的操作的抽象描述。

l  启动一个特定的Activity，代码如下：

   1:  Intent intent=new Intent(CurrentActivity.this,OtherActivity.class);

   2:  startActivity (intent);

其中CurrentActivity是当前的Activity，OtherActivity是要启动的那个Activity，这就类似于窗体之间的跳转，只不过和.NET不同的是指明了谁在新“窗体”之前（或者说谁产生了新“窗体”）。

l  启动一个未指明的Activity，代码如下：

   1:  Intent intent=new Intent(Intent.ACTION_DIAL,Uri.parse("tel:115-1345"));

   2:  startActivity(intent);

以上代码没有指明要启动那个Activity只是把要启动的那个Activity的描述放在了Intent中，让系统去查找符合这个描述的Activity，然后启动并执行。

l  处理一个Activity的返回值，界面设计以及代码如下：

ActivityMain：

   1:  package com.eoeAndroid.activity;

   2:  import android.app.Activity;

   3:  import android.content.Intent;

   4:  import android.net.Uri;

   5:  import android.os.Bundle;

   6:  import android.view.View;

   7:  import android.view.View.OnClickListener;

   8:  import android.widget.Button;

   9:  public class ActivityMain extends Activity

  10:  {

  11:      OnClickListener listener1=null;

  12:      OnClickListener listener2=null;

  13:      Button button1;

  14:      Button button2;

  15:      static final int REQUEST_CODE=1;

  16:      @Override

  17:      public void onCreate(Bundle savedInstanceState)

  18:      {

  19:          super.onCreate(savedInstanceState);

  20:          listener1=new OnClickListener()

  21:          {            

  22:              @Override

  23:              public void onClick(View v)

  24:              {

  25:                  Intent intent1=new Intent(ActivityMain.this,Activity1.class);

  26:                  intent1.putExtra("activityMain", "数据来自activityMain");

  27:                  startActivityForResult(intent1, REQUEST_CODE);

  28:              }

  29:          };        

  30:          listener2 =new OnClickListener()

  31:          {            

  32:              @Override

  33:              public void onClick(View v)

  34:              {

  35:                  setTitle("这是在ActivityMain");

  36:                  Intent intent2=new Intent(ActivityMain.this,Activity2.class);

  37:                  startActivity(intent2);

  38:              }

  39:          };

  40:          setContentView(R.layout.main);

  41:          button1=(Button)findViewById(R.id.button1);

  42:          button1.setOnClickListener(listener1);

  43:          button2=(Button)findViewById(R.id.button2);

  44:          button2.setOnClickListener(listener2);

  45:          setTitle("ActivityMain");

  46:      }

  47:      @Override

  48:      protected void onActivityResult(int requestCode,int resuleCode,Intent data)

  49:      {

  50:          if (requestCode==REQUEST_CODE)

  51:          {

  52:              if (resuleCode==RESULT_CANCELED)

  53:                  setTitle("取消");

  54:              else if (resuleCode==RESULT_OK)

  55:              {

  56:                  String temp=null;

  57:                  Bundle extras=data.getExtras();

  58:                  if (extras!=null)

  59:                  {

  60:                      temp=extras.getString("stroe");

  61:                  }

  62:                  setTitle(temp);            

  63:              }        

  64:          }

  65:      }

  66:  }

Activity1：

   1:  package com.eoeAndroid.activity;

   2:  import android.app.Activity;

   3:  import android.content.Intent;

   4:  import android.os.Bundle;

   5:  import android.view.View;

   6:  import android.view.View.OnClickListener;

   7:  import android.widget.Button;

   8:  public class Activity1 extends Activity {

   9:      OnClickListener listener1 = null;

  10:      Button button1;

  11:      /** Called when the activity is first created. */

  12:      @Override

  13:      public void onCreate(Bundle savedInstanceState) {

  14:          super.onCreate(savedInstanceState);

  15:          setContentView(R.layout.activity1);

  16:          listener1 = new OnClickListener() {

  17:              public void onClick(View v) {

  18:                  Bundle bundle = new Bundle();

  19:                  bundle.putString("store", "数据来自Activity1");

  20:                  Intent mIntent = new Intent();

  21:                  mIntent.putExtras(bundle);

  22:                  setResult(RESULT_OK, mIntent);

  23:                  finish();

  24:              }

  25:          };

  26:          button1 = (Button) findViewById(R.id.button3);

  27:          button1.setOnClickListener(listener1);

  28:          String data=null;

  29:           Bundle extras = getIntent().getExtras();

  30:              if (extras != null) {

  31:                   data = extras.getString("activityMain");

  32:              }

  33:          setTitle("现在是在Activity1里:"+data);

  34:      }

  35:  }

Activity2：

   1:  package com.eoeAndroid.activity;

   2:  import android.app.Activity;

   3:  import android.os.Bundle;

   4:  import android.view.View;

   5:  import android.view.View.OnClickListener;

   6:  import android.widget.Button;

   7:  public class Activity2 extends Activity {

   8:      OnClickListener listener = null;

   9:      Button button;

  10:      /** Called when the activity is first created. */

  11:      @Override

  12:      public void onCreate(Bundle savedInstanceState) {

  13:          super.onCreate(savedInstanceState);

  14:          setContentView(R.layout.activity2);

  15:          listener = new OnClickListener() {

  16:              public void onClick(View v) {

  17:                  finish();

  18:              }

  19:          };

  20:          button = (Button) findViewById(R.id.button4);

  21:          button.setOnClickListener(listener);

  22:          setTitle("现在是在Activity2里");

  23:      }

  24:  }