一起学Android之Intent

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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：

用来激活启动其他应用程序的组件。
作为传递数据和事件的桥梁。

Intent调用模式

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。
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);
}
}