我必须创建一个带有渐变填充的彩色按钮（从沿 Y 轴的按钮中间开始）。如果我将按钮的背景属性设置为我想要的颜色，我会失去按钮的圆润外观和渐变填充（看起来像TextView带背景的）。
另外，我希望在用户按下按钮时改变这种颜色。我可以通过选择器 XML（颜色状态列表）指定这个吗？
感谢任何可以帮助我的教程或链接。
谢谢。
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2 回答
8
我相信您想要做的是让您的按钮在正常状态、按下状态、聚焦状态等下显示不同的渐变。这可以使用 XML 来完成（在 res/drawable 中创建一个 selector.xml 文件以引用res/drawable 中的 shape.xml 文件，每个文件都包含一个渐变元素，然后将按钮的背景设置为您创建的 selector.xml 文件。）但是，XML 路由仅允许您使用两个（或可选的三个）定义渐变) 静态颜色，并且无法控制颜色停止点的位置。程序化解决方案将为您提供更大的灵活性，并允许您动态更改颜色。这是一个名为 GradientLab 的 Android 项目的示例。
资源/布局中的 main.xml：
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
style="@style/LayoutArea"
>
<TextView
style="@style/LayoutRow"
android:text="@string/hello" />
<Button
style="@style/RowButton"
android:id="@+id/btn1"
android:text="1" />
<Button
style="@style/RowButton"
android:id="@+id/btn2"
android:text="2" />
<Button
style="@style/RowButton"
android:id="@+id/btn3"
android:text="3" />
</LinearLayout>
res/values 中的styles.xml：
<?xml version="1.0" encoding="utf-8"?>
<resources>
<style name="LayoutArea">
<item name="android:layout_width">fill_parent</item>
<item name="android:layout_height">fill_parent</item>
</style>
<style name="LayoutRow">
<item name="android:layout_width">fill_parent</item>
<item name="android:layout_height">wrap_content</item>
</style>
<style name="LayoutColumn">
<item name="android:layout_width">wrap_content</item>
<item name="android:layout_height">fill_parent</item>
</style>
<style name="LayoutItem">
<item name="android:layout_width">wrap_content</item>
<item name="android:layout_height">wrap_content</item>
</style>
<style name="RowButton" parent="LayoutRow">
<item name="android:layout_weight">1</item>
<item name="android:layout_margin">8dp</item>
<item name="android:gravity">center_horizontal</item>
</style>
</resources>
android.examples 中的 GradientLab.java 演示了使用带有按钮的渐变：
package android.example;
import android.app.Activity;
import android.graphics.Color;
import android.os.Bundle;
import android.widget.Button;
import android.widget.LinearLayout;
public class GradientLab extends Activity {
// Layout fields
protected LinearLayout mainLayout;
public static Button btn1 = null;
public static Button btn2 = null;
public static Button btn3 = null;
// Members
private int[] normalColors = new int[4];
private int[] focusedColors = new int[2];
private int[] disabledColors = new int[1];
private int defaultSkinR = 94;
private int defaultSkinG = 128;
private int defaultSkinB = 219;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
/*
* This creates View objects from the xml file. The xml file should
* define all views and all static attributes.
*/
mainLayout = (LinearLayout) getLayoutInflater().inflate(R.layout.main,
null);
normalColors[0] = Color.argb(255, defaultSkinR, defaultSkinG,
defaultSkinB);
normalColors[1] = Color.argb(255, 217, 217, 217);
normalColors[2] = Color.argb(191, defaultSkinR, defaultSkinG,
defaultSkinB);
normalColors[3] = Color.argb(140, defaultSkinR, defaultSkinG,
defaultSkinB);
focusedColors[0] = Color.argb(229, 242, 242, 242);
focusedColors[1] = Color.BLUE;
UIGradientSelector gradientSelector1 = new UIGradientSelector(
normalColors, focusedColors, null);
UIGradientSelector gradientSelector2 = new UIGradientSelector(
normalColors, focusedColors, null);
disabledColors[0] = Color.argb(153, 216, 216, 216);
UIGradientDrawable disabledGradient = new UIGradientDrawable(
disabledColors);
btn1 = (Button) mainLayout.findViewById(R.id.btn1);
btn1.setBackgroundDrawable(gradientSelector1);
btn2 = (Button) mainLayout.findViewById(R.id.btn2);
btn2.setBackgroundDrawable(gradientSelector2);
btn3 = (Button) mainLayout.findViewById(R.id.btn3);
btn3.setBackgroundDrawable(disabledGradient);
setContentView(mainLayout);
}
}
android.examples 中的 UIGradientSelector.java 根据按钮状态选择渐变：
package android.example;
import android.graphics.drawable.StateListDrawable;
/**
* {@link StateListDrawable} that controls selection of
* {@link UIGradientDrawable} based on the three basic button states.
*/
public class UIGradientSelector extends StateListDrawable {
/**
* {@link UIGradientSelector} that selects the {@link UIGradientDrawable}
* defined by the colors for the three basic button states.
*
* @param normalColors
* Array of primitive ints that define the gradient colors for a
* button in its normal state.
* @param focusedColors
* Array of primitive ints that define the gradient colors for a
* button in its focused state.
* @param pressedColors
* Array of primitive ints that define the gradient colors for a
* button in its pressed state. If the array is null, then
* focusedColors will be used for the pressed state.
*/
public UIGradientSelector(int[] normalColors, int[] focusedColors,
int[] pressedColors) {
int stateFocused = android.R.attr.state_focused;
int statePressed = android.R.attr.state_pressed;
UIGradientDrawable normalGradient = new UIGradientDrawable(normalColors);
UIGradientDrawable focusedGradient = new UIGradientDrawable(
focusedColors);
UIGradientDrawable pressedGradient;
if (pressedColors == null) {
pressedGradient = focusedGradient;
} else {
pressedGradient = new UIGradientDrawable(pressedColors);
}
addState(new int[] { stateFocused }, focusedGradient);
addState(new int[] { statePressed }, pressedGradient);
addState(new int[] { -statePressed, -stateFocused }, normalGradient);
}
}
绘制表面的 android.examples 中的 UIGradientDrawable.java：
package android.example;
import android.graphics.drawable.PaintDrawable;
import android.graphics.drawable.shapes.RectShape;
/**
* {@link PaintDrawable} that paints the surface via a {@link UIGradientShader}.
*/
public class UIGradientDrawable extends PaintDrawable {
/**
* {@link UIGradientDrawable} with an initial shape of a rounded rectangle
* that transitions evenly between the specified colors.
*
* @param colors
* Array of primitive ints that contain the argb values of the
* color to use for transitioning.
*/
public UIGradientDrawable(int[] colors) {
UIGradientShader gradientShader = new UIGradientShader(colors);
setShape(new RectShape());
setCornerRadius(8);
setShaderFactory(gradientShader);
setDither(true);
}
}
android.examples 中的 UIGradientShader.java 处理实际的转换：
package android.example;
import android.graphics.Color;
import android.graphics.LinearGradient;
import android.graphics.Shader;
import android.graphics.drawable.ShapeDrawable.ShaderFactory;
/**
* {@link ShaderFactory} that uses a {@link LinearGradient} to transition
* between specified colors. Any number of colors may be specified.
*/
public class UIGradientShader extends ShaderFactory {
private int[] colors;
private float[] positions;
/**
* {@link UIGradientShader} that spaces color transitions evenly across the
* painting surface.
*
* @param colors
* Array of primitive ints that contain the argb values of the
* color to use for transitioning. If the array contains only one
* color, then an argb of (0, 0, 0, 0) will be used for the end
* color of the transition. If the array is set to null or
* contains zero colors, then the transition will be from an argb
* of (255, 255, 255, 255) to and argb of (0, 0, 0, 0).
*
* @see Color
*/
public UIGradientShader(int[] colors) {
init(colors, null);
}
/**
* {@link UIGradientShader} that spaces color transitions across the
* painting surface as specified.
*
* @param colors
* Array of primitive ints that contain the argb values of the
* color to use for transitioning. If the array contains only one
* color, then an argb of (0, 0, 0, 0) will be used for the end
* color of the transition. If the array is set to null or
* contains zero colors, then the transition will be from an argb
* of (255, 255, 255, 255) to and argb of (0, 0, 0, 0).
* @param positions
* Array of primitive floats that contain the position of the
* transition points. If the array is null, then the color
* transitions will be spaced evenly.
*/
public UIGradientShader(int[] colors, float[] positions) {
init(colors, positions);
}
private void init(int[] colors, float[] positions) {
if (colors == null || colors.length == 0) {
this.colors = new int[2];
this.colors[0] = Color.argb(255, 255, 255, 255);
this.colors[1] = Color.argb(0, 0, 0, 0);
} else if (colors.length == 1) {
this.colors = new int[2];
this.colors[0] = colors[0];
this.colors[1] = Color.argb(0, 0, 0, 0);
} else {
this.colors = colors;
}
this.positions = positions;
}
public Shader resize(int width, int height) {
LinearGradient lg = new LinearGradient(0, 0, 0, height, colors,
positions, Shader.TileMode.REPEAT);
return lg;
}
}
于 2011-03-23T16:10:36.657 回答
5
您将需要定义一个自定义StateListDrawable资源，可能是从默认情况下 Android 用于按钮的那个克隆而来，您可以在其中将九个补丁图像更改为渐变。您也许可以在 XML 中定义这些渐变，这意味着它们可以很好地伸展。
于 2010-03-08T13:28:58.013 回答