自定义控件——视图的构建过程——视图的构造方法

àì夳堔傛蜴生んèń 2024-04-07 12:36 24阅读 0赞

视图基类View有四个构造方法，分别是：

(1)带一个参数的构造方法public View(Context context)(2)带两个参数的构造方法public View(Context context, AttributeSet attrs)(3)带三个参数的构造方法public View(Context context, AttributeSet attrs, int defStyleAttr)(4)带四个参数的构造方法public View(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes)

构造方法的四个参数说明如下：(1)Context context，视图的上下文(2)AttributeSet attrs，视图的属性设置(3)int defStyleAttr，默认的样式属性(4) int defStyleRes，默认的样式资源

styles.xml定义的样式风格允许用在多个地方，这些地方的优先级顺序为：style属性>defStyleAttr>defStyleRes

===========================================================================================

第一个，系统默认的button

![b82e48efb60f8f4106e654cb033f505b.png][]

第二个，来自style的button

![f63d43dfa10605dd6b698ef100d986e9.png][]

![de0b85aaa1046c6286e5b96ae33e8a6b.png][]

第三个，自定义样式

![8be0b07d1ac65cc2a16cedbeb2c3a033.png][]

第三个参数：defStyleAttr，指定默认的样式属性：

<?xml version="1.0" encoding="utf-8"?>
    <resources>
    
        <declare-styleable name="CustomButton">
            <attr name="customButtonStyle" format="reference" />
        </declare-styleable>
    
    </resources>

![7fa24d16ee184361bd38f7e0f430f145.png][]

<resources>
    
        
        <style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">
            
            <item name="colorPrimary">@color/colorPrimary</item>
            <item name="colorPrimaryDark">@color/colorPrimaryDark</item>
            <item name="colorAccent">@color/colorAccent</item>
            <item name="customButtonStyle">@style/CommonButton</item>
        </style>
    
    
    
    
        <style name="CommonButton">
            <item name="android:textAllCaps">false</item>
            <item name="android:textColor">#000000</item>
            <item name="android:textSize">20sp</item>
        </style>
    
    </resources>

![7eef2595bf850169af84139779d4eaef.png][]

代码：

package com.example.myapplication.widget;
    
    import android.annotation.SuppressLint;
    import android.content.Context;
    import android.util.AttributeSet;
    import android.util.Log;
    import android.widget.Button;
    import com.example.myapplication.R;
    
    @SuppressLint("AppCompatCustomView")
    public class CustomButton extends Button
    {
        private final static String TAG = "CustomButton";
    
        public CustomButton(Context context)
        {
            super(context);
            Log.d(TAG, "只有一个输入参数");
        }
    
        public CustomButton(Context context, AttributeSet attrs)
        {
            this(context, attrs, R.attr.customButtonStyle);
            Log.d(TAG, "有两个输入参数");
        }
    
        public CustomButton(Context context, AttributeSet attrs, int defStyleAttr)
        {
            // 使defStyleAttr奏效的三个条件：
            // 1、attrs.xml增加定义风格属性(如customButtonStyle)，且format值为reference
            // 2、styles.xml增加某种风格的样式定义(如CommonButton)
            // 3、AndroidManifest.xml的application节点的android:theme指定了哪个主题(如AppTheme)，就在该主题内部补充风格属性与样式的对应关系，如
            // <item name="customButtonStyle">@style/CommonButton</item>
            //super(context, attrs, defStyleAttr); // 设置默认的样式属性
            // 下面不使用defStyleAttr，直接使用R.style.CommonButton定义的样式
            this(context, attrs, 0, R.style.CommonButton);
            Log.d(TAG, "有三个输入参数");
    
        }
    
        @SuppressLint("NewApi")
        public CustomButton(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes)
        {
            super(context, attrs, defStyleAttr, defStyleRes);
            Log.d(TAG, "有四个输入参数");
    
        }
    }

![5352db9399394634f1e4c6c20fd52968.png][]

![5f26c871274be988c2c9736219e6e209.png][]

![0b12ffb8ced1ac063e2f34175085a14a.png][]

![9dade3ec40a29f629f0e2dae5245c35d.png][]

![ef8ff5c7a77692c75b8ba1853d0af30d.png][]

![823b1b97311787c2d6965debddcc7ced.png][]

![1694dee99712e441c040312ec5595ca8.png][]

![964cb85a80f1a7a8c873aac1300235d8.png][]

![7b905612bdda8bd47afd160d9daf24d1.png][]

![2bbb6870d6f86bdc7b3146599ed6da5e.png][]

![81ff327cf3011fcf709a4f9bb64dc4f3.png][]

[b82e48efb60f8f4106e654cb033f505b.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/07/eb49dfa6a6a243b5a95bd73f281ed9cd.png
[f63d43dfa10605dd6b698ef100d986e9.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/07/82ef4a36ae244442ad8a9b57857768f7.png
[de0b85aaa1046c6286e5b96ae33e8a6b.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/07/d09a2b4e1cda45619a43a021368b7957.png
[8be0b07d1ac65cc2a16cedbeb2c3a033.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/07/91eeb3155c5c4e9f86bde920684091cf.png
[7fa24d16ee184361bd38f7e0f430f145.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/07/f8bcaf0015ba4432ba0d8a5f221c571b.png
[7eef2595bf850169af84139779d4eaef.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/07/1cceb536da924fe7bd6642376d266fba.png
[5352db9399394634f1e4c6c20fd52968.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/07/6417212b55ea48d4ad94be56aef2519f.png
[5f26c871274be988c2c9736219e6e209.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/07/24a723a7d40145b091f3bc9753582161.png
[0b12ffb8ced1ac063e2f34175085a14a.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/07/204ac7aa43ac41d0999a78caf5d5d29d.png
[9dade3ec40a29f629f0e2dae5245c35d.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/07/967c0c40625b4ce0aaa54538282e5b09.png
[ef8ff5c7a77692c75b8ba1853d0af30d.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/07/e856b4922a464692956a998229a814b1.png
[823b1b97311787c2d6965debddcc7ced.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/07/63bfdd2c3baa4773bcdf726c0df2795a.png
[1694dee99712e441c040312ec5595ca8.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/07/5d9e1d0f87df42aaad5bebd7f6752f07.png
[964cb85a80f1a7a8c873aac1300235d8.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/07/6e4189e368964702a42097be4bf15bf0.png
[7b905612bdda8bd47afd160d9daf24d1.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/07/663c58e657124fd5b98c1efb13a44fe6.png
[2bbb6870d6f86bdc7b3146599ed6da5e.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/07/92da3eb5afa94edfb9a233e4f22a4648.png
[81ff327cf3011fcf709a4f9bb64dc4f3.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/07/f910343ab0b942cdb063b64877aa2e82.png