屏幕亮度就是直接影响用户以及设备电池的因素之一。 Android设备是智能系统,并且具有用于自动亮度的内置系统。但是大多数情况下,用户未选中此功能,或者默认情况下将其关闭。无论此功能是否存在,设置为打开或关闭,或在任何设备中不存在,开发人员都必须考虑此机会并开发优化的应用程序。在应用程序内部声明的任何内容都可能会对外部空间产生影响,即,如果通过应用程序以编程方式更改了屏幕亮度,则即使退出应用程序后,亮度值也可能保持不变。因此,在用户退出之前,必须尝试回溯原件并进行设置。
我们在哪里可以使用此功能?
- 视频播放器:可以直接从视频播放器逐步增加或减少亮度。
- 游戏:可以直接从游戏逐步增加或减少亮度。
- 图书阅读器应用程序:有时候阅读书籍可能是一种喜怒无常的选择,您可以直接从应用程序中逐步增加或减少亮度。
下面的样本GIF给出得到什么我们将在本文中做的想法。请注意,我们将使用Kotlin语言实施此项目。
方法
步骤1:创建一个新项目
要在Android Studio中创建新项目,请参阅如何在Android Studio中创建/启动新项目。请注意,选择Kotlin作为编程语言。
步骤2:使用AndroidManifest.xml文件
控制设备屏幕的亮度需要更改根设置,为此需要在AndroidManifest.xml文件中声明WRITE_SETTINGS的使用权限。
tools:ignore=”ProtectedPermissions” />
以下是AndroidManifest.xml文件的代码。
XML
XML
Kotlin
import android.content.Context
import android.content.Intent
import android.os.Build
import android.os.Bundle
import android.provider.Settings
import android.widget.Button
import android.widget.Toast
import androidx.annotation.RequiresApi
import androidx.appcompat.app.AppCompatActivity
import java.lang.Math.round
class MainActivity : AppCompatActivity() {
@RequiresApi(Build.VERSION_CODES.M)
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
var brightnessValue = 255
// decrease brightness button
val decBrightness: Button = findViewById(R.id.decreaseBrightness)
decBrightness.setOnClickListener { // Get app context object.
val context = applicationContext
// Check whether has the write settings permission or not.
val settingsCanWrite = hasWriteSettingsPermission(context)
// If do not have then open the Can modify system settings panel.
if (!settingsCanWrite) {
changeWriteSettingsPermission(context)
} else {
// brightness cannot be less than 0 and every click decreases the brightness
// by a value of 10
if (brightnessValue >= 11) {
brightnessValue -= 10
changeScreenBrightness(context, brightnessValue)
// Brightness value (1-255) to percentage and output as a Toast
val k = brightnessValue.toDouble() / 255
Toast.makeText(
applicationContext, "Brightness : ${round(k * 100)}%",
Toast.LENGTH_SHORT
).show()
}
}
}
// increase brightness button
val incBrightness: Button = findViewById(R.id.increaseBrightness)
incBrightness.setOnClickListener {
val context = applicationContext
// Check whether has the write settings permission or not.
val settingsCanWrite = hasWriteSettingsPermission(context)
// If do not have then open the Can modify system settings panel.
if (!settingsCanWrite) {
changeWriteSettingsPermission(context)
} else {
// brightness cannot be more than 255 and every click increases the
// brightness by a value of 10
if (brightnessValue <= 245) {
brightnessValue += 10
changeScreenBrightness(context, brightnessValue)
// Brightness value (1-255) to percentage and output as a Toast
val k = brightnessValue.toDouble() / 255
Toast.makeText(
applicationContext, "Brightness : ${round(k * 100)}%",
Toast.LENGTH_SHORT
).show()
}
}
}
}
// Check whether this app has android write settings permission.
@RequiresApi(Build.VERSION_CODES.M)
private fun hasWriteSettingsPermission(context: Context): Boolean {
var ret = true
// Get the result from below code.
ret = Settings.System.canWrite(context)
return ret
}
// Start can modify system settings panel to let user change the write
// settings permission.
private fun changeWriteSettingsPermission(context: Context) {
val intent = Intent(Settings.ACTION_MANAGE_WRITE_SETTINGS)
context.startActivity(intent)
}
// This function only take effect in real physical android device,
// it can not take effect in android emulator.
private fun changeScreenBrightness(context: Context, screenBrightnessValue: Int) {
// Change the screen brightness change mode to manual.
Settings.System.putInt(
context.contentResolver,
Settings.System.SCREEN_BRIGHTNESS_MODE,
Settings.System.SCREEN_BRIGHTNESS_MODE_MANUAL
)
// Apply the screen brightness value to the system, this will change
// the value in Settings ---> Display ---> Brightness level.
// It will also change the screen brightness for the device.
Settings.System.putInt(
context.contentResolver,
Settings.System.SCREEN_BRIGHTNESS, screenBrightnessValue
)
}
}
步骤3:使用activity_main.xml文件
接下来,转到activity_main.xml文件,该文件代表项目的UI。如图所示,添加两个按钮,一个使亮度值最大,另一个使亮度值最小。以下是activity_main.xml文件的代码。
XML格式
步骤4:使用MainActivity.kt文件
最后,转到MainActivity.kt文件,并参考以下代码。下面是MainActivity.kt文件的代码。在代码内部添加了注释,以更详细地了解代码。
科特林
import android.content.Context
import android.content.Intent
import android.os.Build
import android.os.Bundle
import android.provider.Settings
import android.widget.Button
import android.widget.Toast
import androidx.annotation.RequiresApi
import androidx.appcompat.app.AppCompatActivity
import java.lang.Math.round
class MainActivity : AppCompatActivity() {
@RequiresApi(Build.VERSION_CODES.M)
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
var brightnessValue = 255
// decrease brightness button
val decBrightness: Button = findViewById(R.id.decreaseBrightness)
decBrightness.setOnClickListener { // Get app context object.
val context = applicationContext
// Check whether has the write settings permission or not.
val settingsCanWrite = hasWriteSettingsPermission(context)
// If do not have then open the Can modify system settings panel.
if (!settingsCanWrite) {
changeWriteSettingsPermission(context)
} else {
// brightness cannot be less than 0 and every click decreases the brightness
// by a value of 10
if (brightnessValue >= 11) {
brightnessValue -= 10
changeScreenBrightness(context, brightnessValue)
// Brightness value (1-255) to percentage and output as a Toast
val k = brightnessValue.toDouble() / 255
Toast.makeText(
applicationContext, "Brightness : ${round(k * 100)}%",
Toast.LENGTH_SHORT
).show()
}
}
}
// increase brightness button
val incBrightness: Button = findViewById(R.id.increaseBrightness)
incBrightness.setOnClickListener {
val context = applicationContext
// Check whether has the write settings permission or not.
val settingsCanWrite = hasWriteSettingsPermission(context)
// If do not have then open the Can modify system settings panel.
if (!settingsCanWrite) {
changeWriteSettingsPermission(context)
} else {
// brightness cannot be more than 255 and every click increases the
// brightness by a value of 10
if (brightnessValue <= 245) {
brightnessValue += 10
changeScreenBrightness(context, brightnessValue)
// Brightness value (1-255) to percentage and output as a Toast
val k = brightnessValue.toDouble() / 255
Toast.makeText(
applicationContext, "Brightness : ${round(k * 100)}%",
Toast.LENGTH_SHORT
).show()
}
}
}
}
// Check whether this app has android write settings permission.
@RequiresApi(Build.VERSION_CODES.M)
private fun hasWriteSettingsPermission(context: Context): Boolean {
var ret = true
// Get the result from below code.
ret = Settings.System.canWrite(context)
return ret
}
// Start can modify system settings panel to let user change the write
// settings permission.
private fun changeWriteSettingsPermission(context: Context) {
val intent = Intent(Settings.ACTION_MANAGE_WRITE_SETTINGS)
context.startActivity(intent)
}
// This function only take effect in real physical android device,
// it can not take effect in android emulator.
private fun changeScreenBrightness(context: Context, screenBrightnessValue: Int) {
// Change the screen brightness change mode to manual.
Settings.System.putInt(
context.contentResolver,
Settings.System.SCREEN_BRIGHTNESS_MODE,
Settings.System.SCREEN_BRIGHTNESS_MODE_MANUAL
)
// Apply the screen brightness value to the system, this will change
// the value in Settings ---> Display ---> Brightness level.
// It will also change the screen brightness for the device.
Settings.System.putInt(
context.contentResolver,
Settings.System.SCREEN_BRIGHTNESS, screenBrightnessValue
)
}
}
输出:在模拟器上运行
请注意,在运行该应用程序之前,请确保您已授予所需的权限,否则该应用程序将崩溃。