395 lines
11 KiB
Markdown
395 lines
11 KiB
Markdown
|
## 4.1 Activity生命周期
|
|||
|
|
|
|||
|
|
### 4.1.1 生命周期状态
|
|||
|
|
|
|||
|
|
**启动**状态
|
|||
|
|
`Activity` 的启动状态很短暂，一般情况下，当 `Activity` 启动之后便会进入运行状态。
|
|||
|
|
|
|||
|
|
**运行**状态
|
|||
|
|
`Activity` 在此状态时处于界面最前端，它是可见、有焦点的，可以与用户进行交互，如点击界面中的按钮和在界面上输入信息等。
|
|||
|
|
|
|||
|
|
**暂停**状态
|
|||
|
|
在某些情况下， `ActiVity` 对用户采说仍然可见，但它无法状取集点，用户对它操作没有响应，此时它就处于暂停状态。
|
|||
|
|
|
|||
|
|
**停止**状态
|
|||
|
|
当 `Activity` 完全不可见时，它就处于停止状态。
|
|||
|
|
|
|||
|
|
**销毁**状态
|
|||
|
|
当 `Activity` 处于销毁状态时，将被清理出内存。
|
|||
|
|
|
|||
|
|
### 4.1.2 生命周期方法
|
|||
|
|
|
|||
|
|
(1) onCreate(): Activity创建时调用，通常做一些初始化设置。
|
|||
|
|
|
|||
|
|
(2) onStart(): Activity即将可见时调用。
|
|||
|
|
|
|||
|
|
(3) onResume(): Activity获取焦点时调用。
|
|||
|
|
|
|||
|
|
(4) onPause(): 当前Activity被其他Activity覆盖或屏幕锁屏时调用。
|
|||
|
|
|
|||
|
|
(5) onStop(): Activity对用户不可见时调用。
|
|||
|
|
|
|||
|
|
(6) onDestroy(): Activity销毁时调用。
|
|||
|
|
|
|||
|
|
(7) onRestart(): Activity从停止状态到再次启动时调用。
|
|||
|
|
|
|||
|
|
|
|||
|
|
|
|||
|
|
横竖屏切换会调用 `onDestroy()` 销毁 `Activity`，重新调用 `onCreate()` 方法重建Activity。
|
|||
|
|
|
|||
|
|
通过 `configChanges` 属性进行设置就不会清除输入的信息
|
|||
|
|
|
|||
|
|
```xml
|
|||
|
|
<activity android:name=".MainActivity"
|
|||
|
|
android:configChanges="orientationIkeyboardHidden">
|
|||
|
|
```
|
|||
|
|
|
|||
|
|
当`configChanges`属性设置完成之后，打开程序时同样会调用`onCreate()`,`onStar()`、`onResume()`方法，但是当进行横竖屏切换时不会再执行其他的生命周期方法。
|
|||
|
|
|
|||
|
|
如果希望某一个界面一直处于竖屏或者横屏状态，不随手机的晃动而改变，可以在清单文件中通过设置`Activity`的`screenOrientation`属性完成，示例代码如下：
|
|||
|
|
|
|||
|
|
```xml
|
|||
|
|
竖屏：android:screenOrientation="portrait"
|
|||
|
|
横屏：android:screenOrientation="landscape"
|
|||
|
|
```
|
|||
|
|
|
|||
|
|
|
|||
|
|
|
|||
|
|
## 4.2 Activity的创建、配置、开启和关闭
|
|||
|
|
|
|||
|
|
### 4.2.1 创建 Activity
|
|||
|
|
|
|||
|
|
在包上右击选择
|
|||
|
|
|
|||
|
|
|
|||
|
|
|
|||
|
|
一个页面对应一个布局文件 xml
|
|||
|
|
|
|||
|
|
|
|||
|
|
|
|||
|
|
### 4.2.2 配置Activity
|
|||
|
|
|
|||
|
|
清单文件`AndroidManifest.xml`中会创建对应的 xml ，表示程序页面首选项
|
|||
|
|
|
|||
|
|
```xml
|
|||
|
|
<activity
|
|||
|
|
android:name=".MyActivity"
|
|||
|
|
android:exported="false" />
|
|||
|
|
```
|
|||
|
|
|
|||
|
|
### 4.2.3 开启和关闭Activity
|
|||
|
|
|
|||
|
|
(1)在 `activity_main.xml` 中添加按钮组件
|
|||
|
|
|
|||
|
|
```xml
|
|||
|
|
<Button
|
|||
|
|
android:id="@+id/btn"
|
|||
|
|
android:layout_width="match_parent"
|
|||
|
|
android:layout_height="wrap_content"
|
|||
|
|
android:text="单击跳转MyActivity" />
|
|||
|
|
```
|
|||
|
|
|
|||
|
|
(2)在 `MainActivity` 中为按钮添加单击事件，让其跳转到MyActivity页面
|
|||
|
|
|
|||
|
|
```java
|
|||
|
|
@Override
|
|||
|
|
protected void onCreate(Bundle savedInstanceState) {
|
|||
|
|
super.onCreate(savedInstanceState);
|
|||
|
|
setContentView(R.layout.activity_main);
|
|||
|
|
findViewById(R.id.btn).setOnClickListener(new View.OnClickListener() {
|
|||
|
|
@Override
|
|||
|
|
public void onClick(View view) {
|
|||
|
|
// 跳转到MyActivty
|
|||
|
|
Intent intent= new Intent(MainActivity.this,MyActivity.class);
|
|||
|
|
startActivity(intent);
|
|||
|
|
}
|
|||
|
|
});
|
|||
|
|
}
|
|||
|
|
```
|
|||
|
|
|
|||
|
|
(3)在 `activity_my.xml` 中添加按钮组件
|
|||
|
|
|
|||
|
|
```xml
|
|||
|
|
<Button
|
|||
|
|
android:id="@+id/btn"
|
|||
|
|
android:layout_width="match_parent"
|
|||
|
|
android:layout_height="wrap_content"
|
|||
|
|
android:text="关闭当前页面" />
|
|||
|
|
```
|
|||
|
|
|
|||
|
|
(4)在 `MyActivity` 中为按钮添加单击事件，让其关闭当前页面
|
|||
|
|
|
|||
|
|
```java
|
|||
|
|
public class MyActivity extends AppCompatActivity implements View.OnClickListener {
|
|||
|
|
|
|||
|
|
@Override
|
|||
|
|
protected void onCreate(Bundle savedInstanceState) {
|
|||
|
|
super.onCreate(savedInstanceState);
|
|||
|
|
setContentView(R.layout.activity_my);
|
|||
|
|
findViewById(R.id.btn).setOnClickListener(this);
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
@Override
|
|||
|
|
public void onClick(View view) {
|
|||
|
|
// 关闭当前页面
|
|||
|
|
finish();
|
|||
|
|
}
|
|||
|
|
}
|
|||
|
|
```
|
|||
|
|
|
|||
|
|
## 4.3 Intent与IntentFilter
|
|||
|
|
|
|||
|
|
首先创建三个页面 A 、B、C
|
|||
|
|
|
|||
|
|
在`A`页面中填写两个`Button`按钮，分别通过`显示`、`隐示`跳转至其他页面
|
|||
|
|
|
|||
|
|
```xml
|
|||
|
|
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
|
|||
|
|
xmlns:app="http://schemas.android.com/apk/res-auto"
|
|||
|
|
xmlns:tools="http://schemas.android.com/tools"
|
|||
|
|
android:layout_width="match_parent"
|
|||
|
|
android:layout_height="match_parent"
|
|||
|
|
android:orientation="vertical"
|
|||
|
|
tools:context=".A">
|
|||
|
|
|
|||
|
|
<Button
|
|||
|
|
android:id="@+id/b"
|
|||
|
|
android:layout_width="match_parent"
|
|||
|
|
android:layout_height="wrap_content"
|
|||
|
|
android:text="显示跳转页面B" />
|
|||
|
|
|
|||
|
|
<Button
|
|||
|
|
android:id="@+id/c"
|
|||
|
|
android:layout_width="match_parent"
|
|||
|
|
android:layout_height="wrap_content"
|
|||
|
|
android:text="隐示跳转页面C" />
|
|||
|
|
|
|||
|
|
</LinearLayout>
|
|||
|
|
```
|
|||
|
|
|
|||
|
|
|
|||
|
|
|
|||
|
|
```java
|
|||
|
|
public class A extends AppCompatActivity implements View.OnClickListener {
|
|||
|
|
|
|||
|
|
@Override
|
|||
|
|
protected void onCreate(Bundle savedInstanceState) {
|
|||
|
|
super.onCreate(savedInstanceState);
|
|||
|
|
setContentView(R.layout.activity_a);
|
|||
|
|
findViewById(R.id.b).setOnClickListener(this);
|
|||
|
|
findViewById(R.id.c).setOnClickListener(this);
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
@Override
|
|||
|
|
public void onClick(View view) {
|
|||
|
|
switch (view.getId()) {
|
|||
|
|
case R.id.b:
|
|||
|
|
// 显示跳转到B
|
|||
|
|
Intent intent = new Intent(A.this, B.class);
|
|||
|
|
startActivity(intent);
|
|||
|
|
break;
|
|||
|
|
|
|||
|
|
case R.id.c:
|
|||
|
|
// 隐式跳转到C
|
|||
|
|
Intent intent1 = new Intent();
|
|||
|
|
intent1.setAction("a");
|
|||
|
|
startActivity(intent1);
|
|||
|
|
break;
|
|||
|
|
}
|
|||
|
|
}
|
|||
|
|
}
|
|||
|
|
```
|
|||
|
|
|
|||
|
|
更改app入口页面
|
|||
|
|
|
|||
|
|
```xml
|
|||
|
|
<application
|
|||
|
|
android:allowBackup="true"
|
|||
|
|
android:dataExtractionRules="@xml/data_extraction_rules"
|
|||
|
|
android:fullBackupContent="@xml/backup_rules"
|
|||
|
|
android:icon="@mipmap/ic_launcher"
|
|||
|
|
android:label="@string/app_name"
|
|||
|
|
android:roundIcon="@mipmap/ic_launcher_round"
|
|||
|
|
android:supportsRtl="true"
|
|||
|
|
android:theme="@style/Theme.MyApplication"
|
|||
|
|
tools:targetApi="31">
|
|||
|
|
<activity
|
|||
|
|
android:name=".C"
|
|||
|
|
android:exported="false" >
|
|||
|
|
<intent-filter>
|
|||
|
|
<action android:name="a" />
|
|||
|
|
|
|||
|
|
<category android:name="android.intent.category.DEFAULT" />
|
|||
|
|
|
|||
|
|
</intent-filter>
|
|||
|
|
</activity>
|
|||
|
|
<activity
|
|||
|
|
android:name=".B"
|
|||
|
|
android:exported="false" />
|
|||
|
|
|
|||
|
|
<activity
|
|||
|
|
android:name=".A"
|
|||
|
|
android:exported="true">
|
|||
|
|
<intent-filter>
|
|||
|
|
<action android:name="android.intent.action.MAIN" />
|
|||
|
|
|
|||
|
|
<category android:name="android.intent.category.LAUNCHER" />
|
|||
|
|
</intent-filter>
|
|||
|
|
</activity>
|
|||
|
|
</application>
|
|||
|
|
</manifest>
|
|||
|
|
```
|
|||
|
|
|
|||
|
|
|
|||
|
|
|
|||
|
|
## 4.4 Activity之间的跳转
|
|||
|
|
|
|||
|
|
### 4.4.2 Activity之间的数据传递
|
|||
|
|
|
|||
|
|
在首页创建两个按钮
|
|||
|
|
|
|||
|
|
```xml
|
|||
|
|
<Button
|
|||
|
|
android:id="@+id/btn1"
|
|||
|
|
android:layout_width="match_parent"
|
|||
|
|
android:layout_height="wrap_content"
|
|||
|
|
android:text="使用 putExtra 传递数据" />
|
|||
|
|
|
|||
|
|
<Button
|
|||
|
|
android:id="@+id/btn2"
|
|||
|
|
android:layout_width="match_parent"
|
|||
|
|
android:layout_height="wrap_content"
|
|||
|
|
android:text="使用 Bundle 传递数据" />
|
|||
|
|
```
|
|||
|
|
|
|||
|
|
方法
|
|||
|
|
|
|||
|
|
```java
|
|||
|
|
public class MainActivity extends AppCompatActivity implements View.OnClickListener {
|
|||
|
|
Button btn1, btn2;
|
|||
|
|
|
|||
|
|
@Override
|
|||
|
|
protected void onCreate(Bundle savedInstanceState) {
|
|||
|
|
super.onCreate(savedInstanceState);
|
|||
|
|
setContentView(R.layout.activity_main);
|
|||
|
|
btn1 = findViewById(R.id.btn1);
|
|||
|
|
btn1.setOnClickListener(this);
|
|||
|
|
btn2 = findViewById(R.id.btn2);
|
|||
|
|
btn2.setOnClickListener(this);
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
@Override
|
|||
|
|
public void onClick(View view) {
|
|||
|
|
switch (view.getId()) {
|
|||
|
|
case R.id.btn1:
|
|||
|
|
// 使用 putExtra 传递数据
|
|||
|
|
Intent intent = new Intent(MainActivity.this, FirstActivity.class);
|
|||
|
|
intent.putExtra("name", "王小明");
|
|||
|
|
intent.putExtra("age", 12);
|
|||
|
|
intent.putExtra("isPassed", true);
|
|||
|
|
startActivity(intent);
|
|||
|
|
break;
|
|||
|
|
case R.id.btn2:
|
|||
|
|
// 使用 Bundle 传递数据
|
|||
|
|
Intent intent1 = new Intent(MainActivity.this, SecondActivity.class);
|
|||
|
|
|
|||
|
|
// 创建 Bundle 对象
|
|||
|
|
Bundle bundle = new Bundle();
|
|||
|
|
bundle.putString("name","王小明");
|
|||
|
|
bundle.putInt("age",12);
|
|||
|
|
intent1.putExtras(bundle);
|
|||
|
|
startActivity(intent1);
|
|||
|
|
break;
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
}
|
|||
|
|
}
|
|||
|
|
```
|
|||
|
|
|
|||
|
|
另外两个页面
|
|||
|
|
|
|||
|
|
```xml
|
|||
|
|
<Button
|
|||
|
|
android:id="@+id/btn3"
|
|||
|
|
android:layout_width="match_parent"
|
|||
|
|
android:layout_height="wrap_content"
|
|||
|
|
android:text="接收 putExtra 传递的数据" />
|
|||
|
|
|
|||
|
|
<TextView
|
|||
|
|
android:id="@+id/text1"
|
|||
|
|
android:layout_width="match_parent"
|
|||
|
|
android:layout_height="wrap_content" />
|
|||
|
|
```
|
|||
|
|
|
|||
|
|
```xml
|
|||
|
|
<Button
|
|||
|
|
android:id="@+id/btn4"
|
|||
|
|
android:layout_width="match_parent"
|
|||
|
|
android:layout_height="wrap_content"
|
|||
|
|
android:text="接收 Bundle 传递的数据" />
|
|||
|
|
|
|||
|
|
<TextView
|
|||
|
|
android:id="@+id/text2"
|
|||
|
|
android:layout_width="match_parent"
|
|||
|
|
android:layout_height="wrap_content" />
|
|||
|
|
```
|
|||
|
|
|
|||
|
|
接收方法
|
|||
|
|
|
|||
|
|
```java
|
|||
|
|
public class FirstActivity extends AppCompatActivity {
|
|||
|
|
Button btn3;
|
|||
|
|
TextView text1;
|
|||
|
|
|
|||
|
|
@Override
|
|||
|
|
protected void onCreate(Bundle savedInstanceState) {
|
|||
|
|
super.onCreate(savedInstanceState);
|
|||
|
|
setContentView(R.layout.activity_first);
|
|||
|
|
text1=findViewById(R.id.text1);
|
|||
|
|
btn3=findViewById(R.id.btn3);
|
|||
|
|
btn3.setOnClickListener(new View.OnClickListener() {
|
|||
|
|
@Override
|
|||
|
|
public void onClick(View view) {
|
|||
|
|
// 接收数据并显示在text1
|
|||
|
|
Intent intent=getIntent();
|
|||
|
|
String name = intent.getStringExtra("name");
|
|||
|
|
int age = intent.getIntExtra("age",0);
|
|||
|
|
boolean isPassed = intent.getBooleanExtra("isPassed",true);
|
|||
|
|
text1.setText(name+":"+age+":"+isPassed);
|
|||
|
|
}
|
|||
|
|
});
|
|||
|
|
}
|
|||
|
|
}
|
|||
|
|
```
|
|||
|
|
|
|||
|
|
```java
|
|||
|
|
public class SecondActivity extends AppCompatActivity {
|
|||
|
|
Button btn4;
|
|||
|
|
TextView text2;
|
|||
|
|
|
|||
|
|
@Override
|
|||
|
|
protected void onCreate(Bundle savedInstanceState) {
|
|||
|
|
super.onCreate(savedInstanceState);
|
|||
|
|
setContentView(R.layout.activity_second);
|
|||
|
|
text2 = findViewById(R.id.text2);
|
|||
|
|
btn4 = findViewById(R.id.btn4);
|
|||
|
|
btn4.setOnClickListener(new View.OnClickListener() {
|
|||
|
|
@Override
|
|||
|
|
public void onClick(View view) {
|
|||
|
|
// 接收数据并显示在text2
|
|||
|
|
Bundle bundle = getIntent().getExtras();
|
|||
|
|
String name = bundle.getString("name");
|
|||
|
|
int age = bundle.getInt("age");
|
|||
|
|
text2.setText(name + ":" + age);
|
|||
|
|
}
|
|||
|
|
});
|
|||
|
|
|
|||
|
|
}
|
|||
|
|
}
|
|||
|
|
```
|
|||
|
|
|
|||
|
|
|
|||
|
|
|
|||
|
|
### 4.4.2 Activity之间的数据回传
|
|||
|
|
|