如何在安卓中创建循环确定进度栏？
原文:https://www . geeksforgeeks . org/如何创建-循环-确定-android 中的 progress bar/
在本文中，我们将演示如何在安卓工作室中创建一个圆形进度条，显示当前进度值，并且最初具有灰色背景颜色。这里进度显示在栏的中央。下面给出了一个 GIF 示例，来了解一下我们将在本文中做什么。注意，我们将使用 Java 语言来实现这个项目。
逐步实施
第一步:创建新项目
要在安卓工作室创建新项目，请参考如何在安卓工作室创建/启动新项目。请注意，您必须选择 Java 作为编程语言。
步骤 2:创建新的可绘制资源文件
在可绘制文件夹中创建新的可绘制资源文件，名称为 circle.xml 。创建新的可绘制资源文件导航至 res >可绘制并跟随图像
如下所示:
点击可绘制资源文件，一个新的对话框打开，如下图所示。添加文件名，选择根元素作为图层列表，点击确定。
第三步:使用 circle.xml 文件
导航到 res >可绘制> circle.xml 并将下面给出的代码添加到该文件中。在这个文件中，我们将绘制一个显示进度的圆圈。为了更好地理解，代码中添加了注释。
可扩展标记语言
<?xml version="1.0" encoding="utf-8"?>
<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
<!--Adding our first item-->
<item>
<!--Here ring shape is created. The important attribute
used here is, android:useLevel="false". Attribute
with the useLevel=true makes the ring disabled, so it must
be false for the ring to appear with color code "#DDD"-->
<shape
android:shape="ring"
android:thicknessRatio="16"
android:useLevel="false">
<solid android:color="#DDD" />
</shape>
</item>
<!--Adding our second item-->
<item>
<!--Rotation degree of Ring is made from 270 to 270-->
<rotate
android:fromDegrees="270"
android:toDegrees="270">
<!--The main attribute used here is android:useLevel="true" in
shape tag. Also gradient is added to set the startColor and
endColor of the ring.-->
<shape
android:shape="ring"
android:thicknessRatio="16"
android:useLevel="true">
<gradient
android:endColor="@color/teal_700"
android:startColor="@color/black"
android:type="sweep" />
</shape>
</rotate>
</item>
</layer-list>
第四步:给进度条添加样式
导航到 res >布局> theme.xml 并将下面给出的代码添加到该文件中。我们在这个文件中添加了新的样式。为了清楚理解，已适当添加注释。
可扩展标记语言
<resources xmlns:tools="http://schemas.android.com/tools">
<!-- Base application theme. -->
<style name="Theme.ProgressBar" parent="Theme.MaterialComponents.DayNight.DarkActionBar">
<!-- Primary brand color. -->
<item name="colorPrimary">@color/green</item>
<item name="colorPrimaryVariant">@color/green</item>
<item name="colorOnPrimary">@color/white</item>
<!-- Secondary brand color. -->
<item name="colorSecondary">@color/teal_200</item>
<item name="colorSecondaryVariant">@color/teal_700</item>
<item name="colorOnSecondary">@color/black</item>
<!-- Status bar color. -->
<item name="android:statusBarColor" tools:targetApi="l">?attr/colorPrimaryVariant</item>
<!-- Customize your theme here. -->
</style>
<!--Here, android: indeterminateDrawable sets the picture displayed in
the animation or the xml file of this animation and android: indeterminateOnly
This property is set to true,the progress bar will be ignored Progress and present
an infinite loop of animation
-->
<style name="CircularDeterminateProgressBar">
<item name="android:indeterminateOnly">false </item>
<item name="android:progressDrawable">@drawable/circle</item>
</style>
</resources>
第 5 步:使用 activity_main.xml 文件
转到 res >布局> activity_main.xml 并将下面给出的代码添加到该文件中。这里我们添加了一个显示进度的进度栏和一个显示进度百分比的文本视图。还添加了两个按钮来增加或减少进度。代码中添加了必需的注释。
可扩展标记语言
<?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">
<!--Add ProgressBar. Main Attribute used here are
style="@style/CircularDeterminateProgressBar" that
takes style as created in theme.xml file above and
android:progressDrawable="@drawable/circle" that has been
created in circle.xml file above.-->
<ProgressBar
android:id="@+id/progress_bar"
style="@style/CircularDeterminateProgressBar"
android:layout_width="200dp"
android:layout_height="200dp"
android:indeterminateOnly="false"
android:progress="60"
android:progressDrawable="@drawable/circle"
android:rotation="-90"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent"
tools:progress="60" />
<TextView
android:id="@+id/text_view_progress"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textAppearance="@style/TextAppearance.AppCompat.Large"
app:layout_constraintBottom_toBottomOf="@+id/progress_bar"
app:layout_constraintEnd_toEndOf="@+id/progress_bar"
app:layout_constraintStart_toStartOf="@+id/progress_bar"
app:layout_constraintTop_toTopOf="@+id/progress_bar"
tools:text="60%" />
<!--Increment button that will decrement the progress by 10%-->
<Button
android:id="@+id/button_decr"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="- 10%"
app:layout_constraintStart_toStartOf="@+id/progress_bar"
app:layout_constraintTop_toBottomOf="@+id/progress_bar" />
<!--Increment button that will increment the progress by 10%-->
<Button
android:id="@+id/button_incr"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="+ 10%"
app:layout_constraintEnd_toEndOf="@+id/progress_bar"
app:layout_constraintTop_toBottomOf="@+id/progress_bar" />
</androidx.constraintlayout.widget.ConstraintLayout>
步骤 6:使用 MainActivity.java 文件
转到MainActivity.java文件，并将下面给出的代码添加到该文件中。ProgressBar 属性在这里实现。代码中添加了注释，以便快速清晰地理解。
Java 语言(一种计算机语言，尤用于创建网站)
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.ProgressBar;
import android.widget.TextView;
import androidx.appcompat.app.AppCompatActivity;
public class MainActivity extends AppCompatActivity {
private int progress = 0;
Button buttonIncrement;
Button buttonDecrement;
ProgressBar progressBar;
TextView textView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
buttonDecrement = (Button) findViewById(R.id.button_decr);
buttonIncrement = (Button) findViewById(R.id.button_incr);
progressBar = (ProgressBar) findViewById(R.id.progress_bar);
textView = (TextView) findViewById(R.id.text_view_progress);
// when clicked on buttonIncrement progress in increased by 10%
buttonIncrement.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// if progress is less than or equal
// to 90% then only it can be increased
if (progress <= 90) {
progress += 10;
updateProgressBar();
}
}
});
// when clicked on buttonIncrement progress in decreased by 10%
buttonDecrement.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// If progress is greater than
// 10% then only it can be decreased
if (progress >= 10) {
progress -= 10;
updateProgressBar();
}
}
});
}
// updateProgressBar() method sets
// the progress of ProgressBar in text
private void updateProgressBar() {
progressBar.setProgress(progress);
textView.setText(String.valueOf(progress));
}
}
输出:
[https://media.geeksforgeeks.org/wp-content/uploads/20210407101843/WhatsApp-Video-2021-04-07-at-9.02.59-AM.mp4](https://media.geeksforgeeks.org/wp-content/uploads/20210407101843/WhatsApp-Video-2021-04-07-at-9.02.59-AM.mp4)版权属于：月萌API www.moonapi.com，转载请注明出处
