Activity开发要点合集

最新推荐文章于 2023-06-03 16:16:05 发布

原创最新推荐文章于 2023-06-03 16:16:05 发布 · 1.9k 阅读

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本文深入探讨了Android中Activity之间的交互方式，包括显式和隐式Intent的使用方法，以及如何通过onActivityResult回调来处理Activity间的数据传递。同时，还介绍了Activity生命周期中的关键方法及其应用场景。

1.serResult

package cn.itcast.getdata;

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

public class DemoActivity extends Activity {
	EditText et, et2;

	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.main);
		et = (EditText) this.findViewById(R.id.et_contact1);
		et2 = (EditText) this.findViewById(R.id.et_contact2);
	}

	public void click(View view) {
		Intent intent = new Intent(this, ContactActivity.class);
		// startActivity(intent);
		startActivityForResult(intent, 1);
	}

	public void click2(View view) {
		Intent intent = new Intent(this, ContactActivity.class);
		// startActivity(intent);
		startActivityForResult(intent, 2);
	}

	/**
	 * 当被激活的activity 使用完毕 销毁的时候 就会执行onActivityresult的方法
	 */
	@Override
	protected void onActivityResult(int requestCode, int resultCode, Intent data) {
		// TODO Auto-generated method stub
		
		System.out.println("结果码为"+ resultCode);
		super.onActivityResult(requestCode, resultCode, data);

		if (data != null) {
			String name = data.getStringExtra("name");
			if (requestCode == 1) {

				et.setText(name);
			}else if(requestCode == 2){
				et2.setText(name);
			}
			
		}
	}

}

package cn.itcast.getdata;

import java.util.ArrayList;
import java.util.List;

import android.app.Activity;
import android.content.Intent;
import android.database.Cursor;
import android.graphics.Color;
import android.net.Uri;
import android.os.Bundle;
import android.view.View;
import android.view.ViewGroup;a
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.BaseAdapter;
import android.widget.ListView;
import android.widget.TextView;

public class ContactActivity extends Activity {
	ListView lv;
	List<String> names;
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		// TODO Auto-generated method stub
		super.onCreate(savedInstanceState);
		setContentView(R.layout.contact);
		lv = (ListView) this.findViewById(R.id.lv);
		names = getContacts();
		lv.setAdapter(new MyAdapter());
		
		lv.setOnItemClickListener(new OnItemClickListener() {

			@Override
			public void onItemClick(AdapterView<?> parent, View view,
					int position, long id) {
				TextView tv = (TextView) view;
				String name = tv.getText().toString();
				Intent data = new Intent();
				data.putExtra("name", name);
				setResult(3, data);
				// 可以把当前的activity给结束掉 
				finish();
			}
		});
		
	}
	private class MyAdapter extends BaseAdapter{

		@Override
		public int getCount() {
			// TODO Auto-generated method stub
			return names.size();
		}

		@Override
		public Object getItem(int position) {
			// TODO Auto-generated method stub
			return position;
		}

		@Override
		public long getItemId(int position) {
			// TODO Auto-generated method stub
			return position;
		}

		@Override
		public View getView(int position, View convertView, ViewGroup parent) {
			TextView tv = new TextView(ContactActivity.this);
			tv.setTextSize(28);
			tv.setTextColor(Color.RED);
			tv.setText(names.get(position));
			return tv;
		}
		
	}

	private List<String> getContacts (){
		String rawbase = "content://com.android.contacts/raw_contacts";
		String database = "content://com.android.contacts/data";
		Cursor cursor = this.getContentResolver().query(Uri.parse(rawbase), null, null, null, null);
		List<String> names = new ArrayList<String>();
		while (cursor.moveToNext()) {
			
			String id  = cursor.getString( cursor.getColumnIndex("_id"));
			System.out.println("id ="+ id);
			
			Cursor datacursor = this.getContentResolver().query(Uri.parse(database), null, "raw_contact_id=?", new String[]{id}, null);
			while (datacursor.moveToNext()) {
				


				String type = datacursor.getString(datacursor.getColumnIndex("mimetype"));

				
				if("vnd.android.cursor.item/name".equals(type)){
					String data1 = datacursor.getString( datacursor.getColumnIndex("data1"));
					names.add(data1);
					
				}
				
			}
			datacursor.close();
		
		}
		cursor.close();
		return names;
	}
	
	
}

2.跳转Activity

package cn.itcast.mutileactivity;

import android.app.Activity;
import android.content.ComponentName;
import android.content.Intent;
import android.net.Uri;
import android.os.Bundle;
import android.view.View;

public class Demo1Activity extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
    }
    
    
    public void open(View view){
    	// intent 意图 , 描述一个动作, 激活一个组件 
    /*	第一种写法 
     * Intent intent = new Intent();
    	intent.setClassName("cn.itcast.mutileactivity", "cn.itcast.mutileactivity.Demo2Activity");*/
     // 第二种写法 
     //	Intent intent = new Intent(this,Demo2Activity.class);
        /*
         *第三种写法 
    	Intent intent = new Intent();
    	ComponentName  component = new ComponentName("cn.itcast.mutileactivity", "cn.itcast.mutileactivity.Demo2Activity");
    	intent.setComponent(component);
    	*/
    	//前面的三种写法 要求必须要知道 被激活的组件的包名和 class的名字 
    	//显示意图 
    	//****************************************************
//    	Intent intent = new Intent();
//    	intent.setAction("cn.itcast.mutileactivity.xxx");
//    	intent.addCategory("android.xxx");
//    	intent.setData(Uri.parse("itcast://cn.itcast.demo"));
    	//intent.setType(type);  // mime 数据类型 image/jpeg
    	// 隐式意图 
    	// 只需要指定 intent的动作 ,intent的数据  
    	// 如果我们想激活另外一个应用程序的组件 
//    	Intent intent = new Intent();
//    	intent.setAction(Intent.ACTION_PICK);
//    	
//    	intent.setType("image/jpeg");
    	
    	// intent 要去做一件事  泡 动作 泡茶 泡咖啡 泡妞 打人  打酱油 
    	// intent.setData();指定数据的类型 type 
    	// intent.addCategory();
    	/**
    	 *    <intent-filter>
                <action android:name="android.intent.action.VIEW" />
                <category android:name="android.intent.category.DEFAULT" />
                <data android:mimeType="vnd.android-dir/mms-sms" />
            </intent-filter>
    	 */
/*    	Intent intent = new Intent();
    	intent.setAction(Intent.ACTION_VIEW);
    	intent.addCategory("android.intent.category.DEFAULT");
    	intent.setType("vnd.android-dir/mms-sms");*/
    	/**
    	 *             <intent-filter>
                <action android:name="android.intent.action.VIEW" />
                <action android:name="android.intent.action.SENDTO" />
                <category android:name="android.intent.category.DEFAULT" />
                <category android:name="android.intent.category.BROWSABLE" />
                <data android:scheme="sms" />
                <data android:scheme="smsto" />
            </intent-filter>
    	 */
    	
    	Intent intent = new Intent();
    	intent.setAction("android.intent.action.SENDTO");
    	intent.addCategory("android.intent.category.DEFAULT");
    	intent.setData(Uri.parse("smsto:123456"));
    	startActivity(intent);
    }
}

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="cn.itcast.mutileactivity"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk android:minSdkVersion="8" />

    <application
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name" >
        <activity
            android:label="@string/app_name"
            android:name=".Demo1Activity" >
            <intent-filter >
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity
            android:label="@string/activity02"
            android:name=".Demo2Activity" ><intent-filter >
                <action android:name="cn.itcast.mutileactivity.Demo2Activity" />
                <action android:name="cn.itcast.mutileactivity.xxx" />
                <category android:name="android.intent.category.DEFAULT" />
                <category android:name="android.xxx" />
            </intent-filter>
        </activity>
    </application>

</manifest>

3.onSaveInstance的使用

package cn.itcast.life;

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

/**
 * 什么是生命周期   一个对象 从被创建出来new() 到 被销毁 (垃圾回收)这个过程当前必须执行的方法 
 * 
 * @author zehua
 *
 */
public class DemoActivity extends Activity {
	
	
	public void click(View view){
		Intent intent = new Intent(this,Dmeo2Activity.class);
		startActivity(intent);
	}
	
	/**
	 * activity第一次被创建的时候 执行的方法
	 */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        int page = 0;
        //pdf 阅读器  当前用户读到了第30页 
        if(savedInstanceState!=null){
        	page = savedInstanceState.getInt("page");
        	System.out.println("定位到 第 "+ page+"页");
        }
        
        System.out.println("oncreate");
    }

    
    
    
    /**
     * 在activity被异常 回收的时候 会被执行 
     */
    @Override
	protected void onSaveInstanceState(Bundle outState) {
		
		super.onSaveInstanceState(outState);
		outState.putInt("page", 30);
	}

	/**
     * 用户可见的时候 调用onstart();
     */
	@Override
	protected void onStart() {
		// TODO Auto-generated method stub
		super.onStart();
        System.out.println("onStart");
       // System.out.println("判断是否有暂停的位置 ,从暂停的位置继续播放");
	}

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

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

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

	@Override
	protected void onStop() {
		// TODO Auto-generated method stub
	//	System.out.println("暂停视频播放");
		super.onStop();     
		System.out.println("onStop");
	}

	/**
	 * activity 被销毁的时候 执行的方法 
	 */
	@Override
	protected void onDestroy() {
		// TODO Auto-generated method stub
		super.onDestroy();
        System.out.println("onDestroy");
	}
    
}