Android：圖片背景漸層切換與圖層疊加的實現，

Android：圖片背景漸層切換與圖層疊加的實現，

本例要實現的目的：

1.圖片背景漸層的切換，例如漸層的從紅色切換成綠色。

2.代碼中進行圖層疊加，即把多個Drawable疊加在一起顯示在一個組件之上。

：

代碼很簡單：

（1）布局檔案：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:tools="http://schemas.android.com/tools"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:paddingLeft="@dimen/activity_horizontal_margin"    android:paddingRight="@dimen/activity_horizontal_margin"    android:paddingTop="@dimen/activity_vertical_margin"    android:paddingBottom="@dimen/activity_vertical_margin"    tools:ignore="ContentDescription"    tools:context=".MainActivity">    <ImageView        android:id="@+id/color_iv"        android:layout_width="200dp"        android:layout_height="200dp"        android:layout_centerHorizontal="true"        android:src="@drawable/image_bg_2"        android:layout_margin="20dp" />    <TextView        android:id="@+id/note_text"        android:layout_below="@+id/color_iv"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:textSize="16sp"        android:layout_margin="10dp"        android:text="點擊顏色塊，切換圖片背景" />    <LinearLayout        android:layout_width="match_parent"        android:layout_height="48dip"        android:layout_below="@+id/note_text"        android:layout_marginBottom="8dip"        android:layout_marginLeft="4dip"        android:layout_marginRight="4dip"        android:orientation="horizontal">        <ImageView            android:layout_width="0dip"            android:layout_height="match_parent"            android:layout_margin="4dip"            android:layout_weight="1"            android:background="#99666666"            android:onClick="onColorClicked"            android:tag="#99666666" />        <ImageView            android:layout_width="0dip"            android:layout_height="match_parent"            android:layout_margin="4dip"            android:layout_weight="1"            android:background="#9996AA39"            android:onClick="onColorClicked"            android:tag="#9996AA39" />        <ImageView            android:layout_width="0dip"            android:layout_height="match_parent"            android:layout_margin="4dip"            android:layout_weight="1"            android:background="#99C74B46"            android:onClick="onColorClicked"            android:tag="#99C74B46" />        <ImageView            android:layout_width="0dip"            android:layout_height="match_parent"            android:layout_margin="4dip"            android:layout_weight="1"            android:background="#99F4842D"            android:onClick="onColorClicked"            android:tag="#99F4842D" />        <ImageView            android:layout_width="0dip"            android:layout_height="match_parent"            android:layout_margin="4dip"            android:layout_weight="1"            android:background="#993F9FE0"            android:onClick="onColorClicked"            android:tag="#993F9FE0" />        <ImageView            android:layout_width="0dip"            android:layout_height="match_parent"            android:layout_margin="4dip"            android:layout_weight="1"            android:background="#995161BC"            android:onClick="onColorClicked"            android:tag="#995161BC" />    </LinearLayout></RelativeLayout>

（2）Activity代碼：

package com.sinatj.colorgradientanim;import android.graphics.Color;import android.graphics.drawable.ColorDrawable;import android.graphics.drawable.Drawable;import android.graphics.drawable.LayerDrawable;import android.graphics.drawable.TransitionDrawable;import android.os.Build;import android.os.Handler;import android.support.v7.app.ActionBarActivity;import android.os.Bundle;import android.view.View;import android.widget.ImageView;public class MainActivity extends ActionBarActivity {    private ImageView imageView;    private Drawable oldBackground = null;    private Drawable bgDrawable;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        imageView = (ImageView) findViewById(R.id.color_iv);        bgDrawable = getResources().getDrawable(R.drawable.image_bg_1);        //初始顏色        changeColor(Color.parseColor("#6696AA39"));    }    private void changeColor(int newColor) {        Drawable colorDrawable = new ColorDrawable(newColor);        //圖層疊加        LayerDrawable ld = new LayerDrawable(new Drawable[]{bgDrawable, colorDrawable});        if (oldBackground == null) {            imageView.setBackgroundDrawable(ld);        } else {            //漸層切換            TransitionDrawable td = new TransitionDrawable(new Drawable[]{oldBackground, ld});            imageView.setBackgroundDrawable(td);            td.startTransition(300);        }        oldBackground = ld;    }    public void onColorClicked(View v) {        int color = Color.parseColor(v.getTag().toString());        changeColor(color);    }}