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：

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

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

package com.eoeAndroid.activity;
import android.app.Activity;
import android.content.Intent;
import android.net.Uri;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
public class ActivityMain extends Activity
{
    OnClickListener listener1=null;
    OnClickListener listener2=null;
    Button button1;
    Button button2;
    static final int REQUEST_CODE=1;
    @Override
    public void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        listener1=new OnClickListener()
        {
            @Override
            public void onClick(View v)
            {
                Intent intent1=new Intent(ActivityMain.this,Activity1.class);
                intent1.putExtra("activityMain", "数据来自activityMain");
                startActivityForResult(intent1, REQUEST_CODE);
            }
        };
        listener2 =new OnClickListener()
        {
            @Override
            public void onClick(View v)
            {
                setTitle("这是在ActivityMain");
                Intent intent2=new Intent(ActivityMain.this,Activity2.class);
                startActivity(intent2);
            }
        };
        setContentView(R.layout.main);
        button1=(Button)findViewById(R.id.button1);
        button1.setOnClickListener(listener1);
        button2=(Button)findViewById(R.id.button2);
        button2.setOnClickListener(listener2);
        setTitle("ActivityMain");
    }
    @Override
    protected void onActivityResult(int requestCode,int resuleCode,Intent data)
    {
        if (requestCode==REQUEST_CODE)
        {
            if (resuleCode==RESULT_CANCELED)
                setTitle("取消");
            else if (resuleCode==RESULT_OK)
            {
                String temp=null;
                Bundle extras=data.getExtras();
                if (extras!=null)
                {
                    temp=extras.getString("stroe");
                }
                setTitle(temp);
            }
        }
    }
}

Activity1：

package com.eoeAndroid.activity;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
public class Activity1 extends Activity {
    OnClickListener listener1 = null;
    Button button1;
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity1);
        listener1 = new OnClickListener() {
            public void onClick(View v) {
                Bundle bundle = new Bundle();
                bundle.putString("store", "数据来自Activity1");
                Intent mIntent = new Intent();
                mIntent.putExtras(bundle);
                setResult(RESULT_OK, mIntent);
                finish();
            }
        };
        button1 = (Button) findViewById(R.id.button3);
        button1.setOnClickListener(listener1);
        String data=null;
         Bundle extras = getIntent().getExtras();
            if (extras != null) {
                 data = extras.getString("activityMain");
            }
        setTitle("现在是在Activity1里:"+data);
    }
}

Activity2：

package com.eoeAndroid.activity;
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
public class Activity2 extends Activity {
    OnClickListener listener = null;
    Button button;
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity2);
        listener = new OnClickListener() {
            public void onClick(View v) {
                finish();
            }
        };
        button = (Button) findViewById(R.id.button4);
        button.setOnClickListener(listener);
        setTitle("现在是在Activity2里");
    }
}