一起学Android之Intent

本文简述在Android开发中Intent的常见应用，仅供学习分享使用。

什么是Intent?

　　Intent负责对应用中一次操作的动作、动作涉及数据、附加数据进行描述，Android则根据此Intent的描述，负责找到对应的组件，将 Intent传递给调用的组件，并完成组件的调用。因此，Intent在这里起着一个媒体中介的作用，专门提供组件互相调用的相关信息，实现调用者与被调用者之间的解耦。【官方文档：An intent is an abstract description of an operation to be performed（执行某操作的抽象描述）】

Intent的用途有哪些？

关联不同的组件：

1. 用来激活启动其他应用程序的组件。
2. 作为传递数据和事件的桥梁。

Intent调用模式

1. 显式Intent：直接指定目标组件的ComponentNamae，适合启动同一个应用中的其他组件，比如在某应用程序内，一个Activity启动一个Service。
2. 隐式Intent：不直接指定目标组件的ComponentName Class，适合启动设备中不同应用中的组件。

隐式Intent常见例子

打开地图：

  //打开地图
     public void open_map(View v) {
         // Map point based on address
         //Uri location = Uri.parse("geo:0,0?q=1600+Amphitheatre+Parkway,+Mountain+View,+California");
         // Or map point based on latitude/longitude
          Uri location = Uri.parse("geo:34.9501439901632,114.95770290767824?z=14"); // z param is zoom level
         Intent mapIntent = new Intent(Intent.ACTION_VIEW, location);
         startActivity(mapIntent);
     }

打开网页：

  //打开指定的网页
     public void open_url(View v){
         Uri webpage = Uri.parse("http://www.baidu.com");
         Intent webIntent = new Intent(Intent.ACTION_VIEW, webpage);
         startActivity(webIntent);
     }

打电话

 //打电话
     public void open_tel(View v){
         Uri number = Uri.parse("tel:10086");
         Intent callIntent = new Intent(Intent.ACTION_DIAL, number);
         startActivity(callIntent);
     }

日历上设置日程

 //设置日历事件
     public void open_calendar(View v){
         Intent calendarIntent = new Intent(Intent.ACTION_INSERT, CalendarContract.Events.CONTENT_URI);
         Calendar beginTime =  Calendar.getInstance();
         beginTime.set(2012, 0, 19, 7, 30);
         Calendar endTime = Calendar.getInstance();
         endTime.set(2012, 0, 19, 10, 30);
         calendarIntent.putExtra(CalendarContract.EXTRA_EVENT_BEGIN_TIME, beginTime.getTimeInMillis());
         calendarIntent.putExtra(CalendarContract.EXTRA_EVENT_END_TIME, endTime.getTimeInMillis());
         calendarIntent.putExtra(CalendarContract.Events.TITLE, "Ninja class");
         calendarIntent.putExtra(CalendarContract.Events.EVENT_LOCATION, "Secret dojo");
         startActivity(calendarIntent);
     }

判断Intent是否有接收App

 public void open_chkintent(View v){
         Intent calendarIntent = new Intent(Intent.ACTION_INSERT, CalendarContract.Events.CONTENT_URI);
         Calendar beginTime =  Calendar.getInstance();
         beginTime.set(2012, 0, 19, 7, 30);
         Calendar endTime = Calendar.getInstance();
         endTime.set(2012, 0, 19, 10, 30);
         calendarIntent.putExtra(CalendarContract.EXTRA_EVENT_BEGIN_TIME, beginTime.getTimeInMillis());
         calendarIntent.putExtra(CalendarContract.EXTRA_EVENT_END_TIME, endTime.getTimeInMillis());
         calendarIntent.putExtra(CalendarContract.Events.TITLE, "Ninja class");
         calendarIntent.putExtra(CalendarContract.Events.EVENT_LOCATION, "Secret dojo");
         PackageManager packageManager = getPackageManager();
         List<ResolveInfo> activities = packageManager.queryIntentActivities(calendarIntent, 0);
         boolean isIntentSafe = activities.size() > 0;
         String msg=isIntentSafe?"有合适的接收":"没有合适的接收";
         Toast.makeText(this,msg,Toast.LENGTH_SHORT).show();
     }

显式调用Intent

显式调用并传递参数

 //打开一个Activity
     public void open_activity_param(View v){
         Intent intent =new Intent(this,OtherActivity.class);
         intent.putExtra("Name","Alan.hsiang");
         intent.putExtra("Age",100);
         intent.putExtra("Sex",true);
         startActivity(intent);
     }

新的Activity获取参数并展示

 Intent intent=getIntent();
         if(intent!=null){
             if( intent.hasExtra("Name")) {
                 String name = intent.getStringExtra("Name");
                 Integer age = intent.getIntExtra("Age", 0);
                 Boolean sex = intent.getBooleanExtra("Sex", true);
                 Log.i("DemoIntent", "onCreate: "+name+"--"+age+"--"+sex+" ");
                 EditText txtName = (EditText) this.findViewById(R.id.txt_name);
                 txtName.setText(name);
                 Log.i("DemoIntent", "onCreate: txtName ");
                 EditText txtAge = (EditText) this.findViewById(R.id.txt_age);
                 txtAge.setText(age.toString());//此处要转换成字符串，否则会被当成id，从而报错
                 Log.i("DemoIntent", "onCreate: txtAge ");
                 RadioButton rbMale = (RadioButton) this.findViewById(R.id.rb_male);
                 RadioButton rbFemale = (RadioButton) this.findViewById(R.id.rb_female);
                 Log.i("DemoIntent", "onCreate: rbButton ");
                 rbMale.setChecked(sex);
                 rbFemale.setChecked(!sex);
             }
         }

备注

Intent的用途还有很多，本文旨在抛砖引玉，希望大家共同学习。