文章目录
准备
IDE：
Android Studio 4.1.1
Build #AI-201.8743.12.41.6953283, built on November 5, 2020
Runtime version: 1.8.0_242-release-1644-b01 amd64
VM: OpenJDK 64-Bit Server VM by JetBrains s.r.o
Windows 10 10.0
Android Virtual Devices：
Name: Pixel_2_API_28
CPU/ABI: Google Play Intel Atom (x86)
Path: C:\Users\86188\.android\avd\Pixel_2_API_28.avd
Target: google_apis_playstore [Google Play] (API level 28)
Skin: pixel_2
SD Card: 512M
fastboot.chosenSnapshotFile:
runtime.network.speed: full
hw.accelerometer: yes
hw.device.name: pixel_2
hw.lcd.width: 1080
hw.initialOrientation: Portrait
image.androidVersion.api: 28
tag.id: google_apis_playstore
hw.mainKeys: no
hw.camera.front: emulated
avd.ini.displayname: Pixel 2 API 28
hw.gpu.mode: auto
hw.ramSize: 1536
PlayStore.enabled: true
fastboot.forceColdBoot: no
hw.cpu.ncore: 4
hw.keyboard: yes
hw.sensors.proximity: yes
hw.dPad: no
hw.lcd.height: 1920
vm.heapSize: 256
skin.dynamic: yes
hw.device.manufacturer: Google
hw.gps: yes
hw.audioInput: yes
image.sysdir.1: system-images\android-28\google_apis_playstore\x86\
showDeviceFrame: yes
hw.camera.back: virtualscene
AvdId: Pixel_2_API_28
hw.lcd.density: 420
hw.arc: false
hw.device.hash2: MD5:55acbc835978f326788ed66a5cd4c9a7
fastboot.forceChosenSnapshotBoot: no
fastboot.forceFastBoot: yes
hw.trackBall: no
hw.battery: yes
hw.sdCard: yes
tag.display: Google Play
runtime.network.latency: none
disk.dataPartition.size: 6442450944
hw.sensors.orientation: yes
avd.ini.encoding: UTF-8
hw.gpu.enabled: yes
注意：以下示例仅在安卓虚拟设备上运行测试，并没有在真实的设备上运行测试。
自定义按钮（Button）点击、获取焦点的背景
新建项目，选择 Empty Activity，在配置项目时，Minimum SDK 选择 API 16: Android 4.1 (Jelly Bean)。
编辑 src\main\AndroidManifest.xml 应用清单文件，修改应用主题（第 5 行）：
<?xml version="1.0" encoding="utf-8"?>
<manifest ...>
<application
...
android:theme="@style/Theme.AppCompat.NoActionBar">
...
</application>
</manifest>
新增 src\main\res\drawable\button_state_pressed.xml 文件：
<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
android:shape="rectangle">
<corners android:radius="5dp" />
<solid android:color="#00000000" />
<stroke android:width="1dp" android:color="#00FF00" />
</shape>
新增 src\main\res\drawable\button_state_focused.xml 文件：
<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
android:shape="rectangle">
<corners android:radius="5dp" />
<solid android:color="#00000000" />
<stroke android:width="1dp" android:color="#0000FF" />
</shape>
新增 src\main\res\drawable\button_state_default.xml 文件：
<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
android:shape="rectangle"> <!-- A rectangle that fills the containing View. This is the default shape. -->
<!-- Creates rounded corners for the shape. Applies only when the shape is a rectangle. -->
<!-- android:radius
Dimension. The radius for all corners, as a dimension value or dimension resource. -->
<corners android:radius="5dp" />
<!-- A solid color to fill the shape. -->
<!-- android:color
Color. The color to apply to the shape, as a hexadecimal value or color resource. -->
<solid android:color="#00000000" />
<!-- A stroke line for the shape. -->
<!-- android:width
Dimension. The thickness of the line, as a dimension value or dimension resource. -->
<!-- android:color
Color. The color of the line, as a hexadecimal value or color resource. -->
<stroke android:width="1dp" android:color="#FF0000" />
</shape>
新增 src\main\res\drawable\button_custom.xml 文件：
<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
<item android:drawable="@drawable/button_state_pressed"
android:state_pressed="true" />
<item android:drawable="@drawable/button_state_focused"
android:state_focused="true" />
<item android:drawable="@drawable/button_state_default" />
</selector>
编辑 src\main\res\layout\activity_main.xml 布局文件：
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout 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"
tools:context=".MainActivity">
<EditText
android:id="@+id/editText"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_marginStart="16dp"
android:layout_marginLeft="16dp"
android:layout_marginTop="16dp"
android:layout_marginEnd="16dp"
android:layout_marginRight="16dp"
android:ems="10"
android:hint="按 Tab 键，将焦点切换到按钮上，注意观察"
android:inputType="textPersonName"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<Button
android:id="@+id/button"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_marginStart="16dp"
android:layout_marginLeft="16dp"
android:layout_marginTop="16dp"
android:layout_marginEnd="16dp"
android:layout_marginRight="16dp"
android:background="@drawable/button_custom"
android:text="Button"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.0"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/editText" />
</androidx.constraintlayout.widget.ConstraintLayout>
编辑 MainActivity 文件：
package com.mk;
import androidx.appcompat.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;
public class MainActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Button button = (Button) findViewById(R.id.button);
button.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Toast.makeText(MainActivity.this, "On Click", Toast.LENGTH_SHORT).show();
}
});
button.setOnFocusChangeListener(new View.OnFocusChangeListener() {
@Override
public void onFocusChange(View v, boolean hasFocus) {
if (hasFocus)
Toast.makeText(MainActivity.this, "On Focus", Toast.LENGTH_SHORT).show();
}
});
}
}