一起學Android之Intent

本文簡述在Android開發中Intent的常見應用，僅供學習分享使用。

什麼是Intent?

　　Intent負責對應用中一次操作的動作、動作涉及數據、附加數據進行描述，Android則根據此Intent的描述，負責找到對應的組件，將 Intent傳遞給調用的組件，並完成組件的調用。因此，Intent在這裡起著一個媒體中介的作用，專門提供組件互相調用的相關信息，實現調用者與被調用者之間的解耦。【官方文檔：An intent is an abstract description of an operation to be performed（執行某操作的抽象描述）】

Intent的用途有哪些？

關聯不同的組件：

1. 用來激活啟動其他應用程式的組件。
2. 作為傳遞數據和事件的橋梁。

Intent調用模式

1. 顯式Intent：直接指定目標組件的ComponentNamae，適合啟動同一個應用中的其他組件，比如在某應用程式內，一個Activity啟動一個Service。
2. 隱式Intent：不直接指定目標組件的ComponentName Class，適合啟動設備中不同應用中的組件。

隱式Intent常見例子

打開地圖：

1  //打開地圖
2     public void open_map(View v) {
3         // Map point based on address
4         //Uri location = Uri.parse("geo:0,0?q=1600+Amphitheatre+Parkway,+Mountain+View,+California");
5         // Or map point based on latitude/longitude
6          Uri location = Uri.parse("geo:34.9501439901632,114.95770290767824?z=14"); // z param is zoom level
7         Intent mapIntent = new Intent(Intent.ACTION_VIEW, location);
8         startActivity(mapIntent);
9     }

打開網頁：

1  //打開指定的網頁
2     public void open_url(View v){
3         Uri webpage = Uri.parse("http://www.baidu.com");
4         Intent webIntent = new Intent(Intent.ACTION_VIEW, webpage);
5         startActivity(webIntent);
6     }

打電話

1 //打電話
2     public void open_tel(View v){
3         Uri number = Uri.parse("tel:10086");
4         Intent callIntent = new Intent(Intent.ACTION_DIAL, number);
5         startActivity(callIntent);
6     }

日曆上設置日程

 1 //設置日曆事件
 2     public void open_calendar(View v){
 3         Intent calendarIntent = new Intent(Intent.ACTION_INSERT, CalendarContract.Events.CONTENT_URI);
 4         Calendar beginTime =  Calendar.getInstance();
 5         beginTime.set(2012, 0, 19, 7, 30);
 6         Calendar endTime = Calendar.getInstance();
 7         endTime.set(2012, 0, 19, 10, 30);
 8         calendarIntent.putExtra(CalendarContract.EXTRA_EVENT_BEGIN_TIME, beginTime.getTimeInMillis());
 9         calendarIntent.putExtra(CalendarContract.EXTRA_EVENT_END_TIME, endTime.getTimeInMillis());
10         calendarIntent.putExtra(CalendarContract.Events.TITLE, "Ninja class");
11         calendarIntent.putExtra(CalendarContract.Events.EVENT_LOCATION, "Secret dojo");
12         startActivity(calendarIntent);
13     }

判斷Intent是否有接收App

 1 public void open_chkintent(View v){
 2         Intent calendarIntent = new Intent(Intent.ACTION_INSERT, CalendarContract.Events.CONTENT_URI);
 3         Calendar beginTime =  Calendar.getInstance();
 4         beginTime.set(2012, 0, 19, 7, 30);
 5         Calendar endTime = Calendar.getInstance();
 6         endTime.set(2012, 0, 19, 10, 30);
 7         calendarIntent.putExtra(CalendarContract.EXTRA_EVENT_BEGIN_TIME, beginTime.getTimeInMillis());
 8         calendarIntent.putExtra(CalendarContract.EXTRA_EVENT_END_TIME, endTime.getTimeInMillis());
 9         calendarIntent.putExtra(CalendarContract.Events.TITLE, "Ninja class");
10         calendarIntent.putExtra(CalendarContract.Events.EVENT_LOCATION, "Secret dojo");
11         PackageManager packageManager = getPackageManager();
12         List<ResolveInfo> activities = packageManager.queryIntentActivities(calendarIntent, 0);
13         boolean isIntentSafe = activities.size() > 0;
14         String msg=isIntentSafe?"有合適的接收":"沒有合適的接收";
15         Toast.makeText(this,msg,Toast.LENGTH_SHORT).show();
16     }

顯式調用Intent

顯式調用並傳遞參數

1 //打開一個Activity
2     public void open_activity_param(View v){
3         Intent intent =new Intent(this,OtherActivity.class);
4         intent.putExtra("Name","Alan.hsiang");
5         intent.putExtra("Age",100);
6         intent.putExtra("Sex",true);
7         startActivity(intent);
8     }

新的Activity獲取參數並展示

 1 Intent intent=getIntent();
 2         if(intent!=null){
 3             if( intent.hasExtra("Name")) {
 4                 String name = intent.getStringExtra("Name");
 5                 Integer age = intent.getIntExtra("Age", 0);
 6                 Boolean sex = intent.getBooleanExtra("Sex", true);
 7                 Log.i("DemoIntent", "onCreate: "+name+"--"+age+"--"+sex+" ");
 8                 EditText txtName = (EditText) this.findViewById(R.id.txt_name);
 9                 txtName.setText(name);
10                 Log.i("DemoIntent", "onCreate: txtName ");
11                 EditText txtAge = (EditText) this.findViewById(R.id.txt_age);
12                 txtAge.setText(age.toString());//此處要轉換成字元串，否則會被當成id，從而報錯
13                 Log.i("DemoIntent", "onCreate: txtAge ");
14                 RadioButton rbMale = (RadioButton) this.findViewById(R.id.rb_male);
15                 RadioButton rbFemale = (RadioButton) this.findViewById(R.id.rb_female);
16                 Log.i("DemoIntent", "onCreate: rbButton ");
17                 rbMale.setChecked(sex);
18                 rbFemale.setChecked(!sex);
19             }
20         }

備註

 Intent的用途還有很多，本文旨在拋磚引玉，希望大家共同學習。