一、排坑
显式意图跳转闪退
应用间不要用显式意图
Activity直接返回到主Activity时闪退
onActivityResult内加入resultcode判断
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
// TODO Auto-generated method stub
super.onActivityResult(requestCode, resultCode, data);
if (resultCode != 1 && resultCode != 2) {
return;
}
String name = data.getStringExtra("name");
if(requestCode == 10){
EditText et = (EditText)findViewById();
et.setText(name);
}
else if(requestCode == 20){
EditText et_content = (EditText)findViewById(_content);
et_content.setText(name);
}
}
二、Activity跳转
Activity的跳转需要创建Intent对象,通过设置intent对象的参数指定要跳转Activity
通过设置Activity的包名和类名实现跳转,称为显式意图
通过指定动作实现跳转,称为隐式意图
显式意图
跳转至同一项目下的另一个Activity,直接指定该Activity的字节码即可
跳转至其他应用中的Activity,需要指定该应用的包名和该Activity的类名
隐式意图
要让一个Activity可以被隐式启动,需要在清单文件的activity节点中设置intent-filter子节点
<intent-filter >
<action android:name="com.itheima.second"/>
<data android:scheme="asd" android:mimeType="aa/bb"/>
<category android:name="android.intent.category.DEFAULT"/>
</intent-filter>action 指定动作(可以自定义,可以使用系统自带的)
data 指定数据(操作什么内容)
category 类别 (默认类别,机顶盒,车载电脑)
隐式意图启动Activity,需要为intent设置以上三个属性,且值必须与该Activity在清单文件中对三个属性的定义匹配
intent-filter节点及其子节点都可以同时定义多个,隐式启动时只需与任意一个匹配即可
显式意图和隐式意图的应用场景
显式意图用于启动同一应用中的Activity
隐式意图用于启动不同应用中的Activity
如果系统中存在多个Activity的intent-filter同时与你的intent匹配,那么系统会显示一个对话框,列出所有匹配的Activity,由用户选择启动哪一个
public class MainActivity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
if (ContextCompat.checkSelfPermission(MainActivity.this,
Manifest.permission.CALL_PHONE)!= PackageManager.PERMISSION_GRANTED){
//申请权限
ActivityCompat.requestPermissions(MainActivity.this,
new String[]{Manifest.permission.CALL_PHONE},1);
}else {
//把动作告诉系统
//send();
}
}
/**
* 跳转至打电话activity
* 跳转至其他应用的activity
* 隐式跳转:通过指定action和data
* @param v
*/
public void click1(View v){
Intent intent = new Intent();
//隐式意图
intent.setAction(Intent.ACTION_CALL);
intent.setData(Uri.parse("tel:110"));
//跳转
startActivity(intent);
}
/**
* 跳转至secondActivity
* 在本应用中跳转
* 显示跳转:直接指定目标Activity的包名和类名
* @param v
*/
public void click2(View v){
Intent intent = new Intent();
//cls:直接指定目标Activity的类名
//显示意图
intent.setClass(this, SecondActivity.class);
startActivity(intent);
}
/**
* 显示跳转至拨号器
*/
//bug!!!
public void click3(View v){
Intent intent = new Intent();
//指定目标Activity的包名和类名
intent.setClassName("com.android.dialer", "com.android.dialer.DialtactsActivity");
startActivity(intent);
}
/**
* 隐式跳转至拨号器
*/
public void click4(View v){
Intent intent = new Intent();
//隐式设置拨号器的动作
intent.setAction(Intent.ACTION_DIAL);
startActivity(intent);
}
/**
* 隐式跳转至secondActivity
* @param v
*/
public void click5(View v){
Intent intent = new Intent();
intent.setAction("com.itheima.sa2");
// intent.setData(Uri.parse("heima2:qwe"));
// intent.setType("text/username");
// intent.setData(Uri.parse("heima2:qwe123"));
intent.setDataAndType(Uri.parse("heima2:qwe123"), "text/username");
//系统会自动添加默认的category
intent.addCategory(Intent.CATEGORY_DEFAULT);
startActivity(intent);
}
/**
* 显式跳转至浏览器
*/
//bug!!!
public void click6(View v){
Intent intent = new Intent();
intent.setClassName("com.android.browser", "com.android.browser.BrowserActivity");
startActivity(intent);
}
/**
* 隐式跳转至浏览器
* @param v
*/
public void click7(View v){
Intent intent = new Intent();
intent.setAction(Intent.ACTION_VIEW);
intent.setData(Uri.parse("http://www.baidu.com"));
startActivity(intent);
}
}public class SecondActivity extends Activity {
private static final String TAG = "SecondActivity";
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_second);
//获取到启动这个activity的意图
Intent intent = getIntent();
Uri uri = intent.getData();
if(uri!=null)
Log.e(TAG, uri.toString());
}
}<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http:///apk/res/android"
package="com.example.index42.createactivity">
<uses-permission android:name="android.permission.CALL_PHONE"/>
<application
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:roundIcon="@mipmap/ic_launcher_round"
android:supportsRtl="true"
android:theme="@style/AppTheme">
<activity android:name=".MainActivity"
android:icon="@drawable/photo2"
android:label="主界面">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity android:name=".SecondActivity"
android:icon="@drawable/photo3"
android:label="第二个界面">
<intent-filter ><action android:name="com.itheima.sa"/>
<action android:name="com.itheima.sa3"/>
<data android:scheme="heima"/>
<data android:scheme="heima3"/>
<category android:name="android.intent.category.DEFAULT"/>
</intent-filter>
<intent-filter >
<action android:name="com.itheima.sa2"/>
<data android:scheme="heima2" android:mimeType="text/username"/>
<category android:name="android.intent.category.DEFAULT"/>
</intent-filter>
</activity>
</application>
</manifest>跳转时的数据传递
public class SecondActivity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_second);
Intent intent = getIntent();
//从intent对象中把封装好的数据取出来
// String maleName = intent.getStringExtra("malename");
// String feMaleName = intent.getStringExtra("femalename");
Bundle bundle = intent.getExtras();
String maleName = bundle.getString("malename");
String feMaleName = bundle.getString("femalename");
Random rd = new Random();
int yinyuan = rd.nextInt(100);
TextView tv = (TextView) findViewById(.tv);
tv.setText(maleName + "和" + feMaleName + "的姻缘值为" + yinyuan);
}
}三、Activity生命周期
void onCreate()
- Activity已经被创建完毕
void onStart()
- Activity已经显示在屏幕,但没有得到焦点
void onResume()
- Activity得到焦点,可以与用户交互
void onPause()
- Activity失去焦点,无法再与用户交互,但依然可见
void onStop()
- Activity不可见,进入后台
void onDestroy()
- Activity被销毁
void onRestart()
- Activity从不可见变成可见时会执行此方法
使用场景
- Activity创建时需要初始化资源,销毁时需要释放资源;或者播放器应用,在界面进入后台时需要自动暂停
完整生命周期(entire lifetime)
onCreate-->onStart-->onResume-->onPause-->onStop-->onDestory
可视生命周期(visible lifetime)
onStart-->onResume-->onPause-->onStop
前台生命周期(foreground lifetime)
onResume-->onPause
四、Activity的四种启动模式
每个应用会有一个Activity任务栈,存放已启动的Activity
Activity的启动模式,修改任务栈的排列情况
- standard 标准启动模式
- singleTop 单一顶部模式
- 如果任务栈的栈顶存在这个要开启的activity,不会重新的创建activity,而是复用已经存在的activity。保证栈顶如果存在,不会重复创建。
- 应用场景:浏览器的书签
- singeTask 单一任务栈,在当前任务栈里面只能有一个实例存在
- 当开启activity的时候,就去检查在任务栈里面是否有实例已经存在,如果有实例存在就复用这个已经存在的activity,并且把这个activity上面的所有的别的activity都清空,复用这个已经存在的activity。保证整个任务栈里面只有一个实例存在
- 应用场景:浏览器的activity
- 如果一个activity的创建需要占用大量的系统资源(cpu,内存)一般配置这个activity为singletask的启动模式。webkit内核 c代码
- singleInstance启动模式非常特殊, activity会运行在自己的任务栈里面,并且这个任务栈里面只有一个实例存在
- 如果你要保证一个activity在整个手机操作系统里面只有一个实例存在,使用singleInstance
- 应用场景: 电话拨打界面
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http:///apk/res/android"
package="com.example.index42.lifecycle">
<application
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:roundIcon="@mipmap/ic_launcher_round"
android:supportsRtl="true"
android:theme="@style/AppTheme">
<activity android:name=".MainActivity">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity android:launchMode="singleInstance"
android:name=".SecondActivity">
</activity>
</application>
</manifest>五、横竖屏切换
默认情况下 ,横竖屏切换, 销毁当前的activity,重新创建一个新的activity
在一些特殊的应用程序场景下,比如游戏,不希望横竖屏切换activity被销毁重新创建
需求:禁用掉横竖屏切换的生命周期
始终横屏,可180度旋转
public class MainActivity extends Activity {
private static final String TAG = "MainActivity";
private SreenOrientationListener mSreenOrientationListener;
int blood;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Log.e(TAG, "main:create" );
//设置当前Activity的方向,使用代码控制横竖屏
setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE);
//setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);
mSreenOrientationListener = new SreenOrientationListener(this);
blood = 100;
}
class SreenOrientationListener extends OrientationEventListener {
public SreenOrientationListener(Context context) {
super(context);
}
@Override
public void onOrientationChanged(int orientation) {
if (orientation == OrientationEventListener.ORIENTATION_UNKNOWN) {
return; // 手机平放时,检测不到有效的角度
}
// 只检测是否有四个角度的改变
if (orientation > 350 || orientation < 10) {
// 0度:手机默认竖屏状态(home键在正下方)
orientation = 0;
setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_REVERSE_LANDSCAPE);
Log.e("orientation", "orientation" + orientation);
} else if (orientation > 80 && orientation < 100) {
// 90度:手机顺时针旋转90度横屏(home建在左侧)
setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_REVERSE_LANDSCAPE);
Log.e("orientation", "orientation" + orientation);
} else if (orientation > 170 && orientation < 190) {
// 手机顺时针旋转180度竖屏(home键在上方)
orientation = 180;
setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE);
Log.e("orientation", "orientation" + orientation);
} else if (orientation > 260 && orientation < 280) {
// 手机顺时针旋转270度横屏,(home键在右侧)
setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE);
Log.e("orientation", "orientation" + orientation);
}
}
}
@Override
protected void onStart() {
// TODO Auto-generated method stub
super.onStart();
System.out.println("main:start");
}
@Override
protected void onResume() {
// TODO Auto-generated method stub
super.onResume();
mSreenOrientationListener.enable();
System.out.println("main:resume");
};
@Override
protected void onPause() {
// TODO Auto-generated method stub
super.onPause();
mSreenOrientationListener.disable();
System.out.println("main:pause");
}
@Override
protected void onStop() {
// TODO Auto-generated method stub
super.onStop();
System.out.println("main:stop");
}
@Override
protected void onDestroy() {
// TODO Auto-generated method stub
super.onDestroy();
System.out.println("main:destroy");
};
@Override
protected void onRestart() {
// TODO Auto-generated method stub
super.onRestart();
System.out.println("main:restart");
}
public void click(View v){
Intent intent = new Intent(this, SecondActivity.class);
startActivity(intent);
}
}<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http:///apk/res/android"
package="com.example.index42.lifecycle">
<application
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:roundIcon="@mipmap/ic_launcher_round"
android:supportsRtl="true"
android:theme="@style/AppTheme">
<activity android:name=".MainActivity"
android:configChanges="orientation|keyboardHidden|screenSize">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name=".SecondActivity">
</activity>
</application>
</manifest>六、Activity跳转返回值
public class MainActivity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
public void click(View c){
//跳转至选择联系人Activity
Intent intent = new Intent(this, ContactActivity.class);
// startActivity(intent);
//用这个api启动的Activity,在销毁时,系统会回调onActivityResult
startActivityForResult(intent, 10);
}
public void click2(View v){
//跳转至选择快捷回复的Activity
Intent intent = new Intent(this, CallbackActivity.class);
startActivityForResult(intent, 20);
}
//如果有Activity在销毁时返回了数据,那么就会调用此方法来接收数据
//requestCode:用来区分数据来自于哪一个Activity
//resultCode:用来区分返回的数据是什么类型的
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
// TODO Auto-generated method stub
super.onActivityResult(requestCode, resultCode, data);
if (resultCode != 1 && resultCode != 2) {
return;
}
String name = data.getStringExtra("name");
if(requestCode == 10){
EditText et = (EditText)findViewById();
et.setText(name);
}
else if(requestCode == 20){
EditText et_content = (EditText)findViewById(_content);
et_content.setText(name);
}
}
}public class ContactActivity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_contact);
ListView lv = (ListView) findViewById(.lv);
final String[] objects = new String[]{
"小志",
"逼哥",
"世界级XXX",
"国服第一"
};
lv.setAdapter(new ArrayAdapter<String>(this, R.layout.item_listview, .tv, objects));
//给listview设置条目的点击侦听
lv.setOnItemClickListener(new OnItemClickListener() {
//当某个条目被点击时,此方法调用
@Override
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
//Activity返回时传递数据,也是通过意图对象
Intent data = new Intent();
//把要传递的数据封装至意图对象中
data.putExtra("name", objects[position]);
//当前Activity销毁时,data这个意图就会传递给启动当前Activity的那个Activity
setResult(1, data);
//销毁当前Activity
finish();
}
});
}
}public class CallbackActivity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_contact);
ListView lv = (ListView) findViewById(.lv);
final String[] objects = new String[]{
"免谈,没戏,滚犊子",
"媳妇我错了,求原谅",
"老子才是一家之主"
};
lv.setAdapter(new ArrayAdapter<String>(this, R.layout.item_listview, .tv, objects));
lv.setOnItemClickListener(new OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
Intent data = new Intent();
data.putExtra("name", objects[position]);
setResult(2, data);
finish();
}
});
}
}<LinearLayout xmlns:android="http:///apk/res/android"
xmlns:tools="http:///tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity"
android:orientation="vertical"
>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal"
>
<EditText
android:id="@+id/et"
android:layout_weight="1"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:hint="请输入联系人"
/>
<Button
android:layout_weight="0"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="+"
android:onClick="click"
/>
</LinearLayout>
<EditText
android:id="@+id/et_content"
android:layout_weight="1"
android:layout_width="match_parent"
android:layout_height="0dp"
android:hint="请输入短信内容"
android:gravity="top"
/>
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="快捷回复"
android:onClick="click2"
/>
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="发送短信"
/>
</LinearLayout><?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http:///apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<TextView
android:id="@+id/tv"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textSize="20sp"
/>
</LinearLayout><?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http:///apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<ListView
android:id="@+id/lv"
android:layout_width="match_parent"
android:layout_height="match_parent"
></ListView>
</LinearLayout>
















