Comment dégradé d'un bouton de fond?

Je crois que ce que vous êtes désireux de le faire est d'avoir vos boutons de montrer les différents gradients lorsque dans l'état normal, l'état enfoncé, concentré de l'état, etc. Cela peut être fait en utilisant le langage XML (Créer un selector.xml fichier dans res/drawable qui fait référence à shape.xml fichiers dans res/drawable, qui contiennent un élément de pente, puis définir l'arrière-plan de votre bouton de la selector.xml le fichier que vous avez créé.) Cependant, le XML route ne vous permettent de définir les dégradés avec deux (ou éventuellement trois) couleurs statiques et sans aucun contrôle sur l'emplacement des points d'arrêt de couleur. Une solution de programmation vont vous donner beaucoup plus de souplesse et de vous permettre de modifier dynamiquement les couleurs. Voici un exemple pour un projet Android appelé GradientLab.

main.xml dans res/layout:

<?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>

styles.xml dans res/valeurs:

<?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>

GradientLab.java dans android.des exemples que des démonstrations de l'utilisation de dégradés avec des boutons:

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);
}
}

UIGradientSelector.java dans android.les exemples qui sélectionne les gradients de base sur l'état du bouton:

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);
}
}

UIGradientDrawable.java dans android.les exemples qui peint la surface:

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);
}
}

UIGradientShader.java dans android.les exemples qui gère les transitions réelles:

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;
}
}

OriginalL'auteur Danny Remington - OMS