Android Custom View

2014-09-01 Kommentare Android

Creating a View Class

在Android中使用Custom View，必須尊崇以下規則

  1. 符合Android的標準
  2. Provide custom styleable attributes that work with Android XML layouts
  3. Send accessibility events
  4. 相容於其他安卓平台

Subclass a View

為了讓Android Developer Tools跟你的view做互動，你必須提供最低限度的建構子並可接受Context和AttributeSet這兩項參數

class PieChart extends View {
    public PieChart(Context context, AttributeSet attrs) {
        super(context, attrs);
    }
}

Define Custom Attributes

接著新增res/values/attrs.xml

attrs.xml
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<resources>
   <declare-styleable name="PieChart">
	   <attr name="showText" format="boolean" />
	   <attr name="labelPosition" format="enum">
		   <enum name="left" value="0"/>
		   <enum name="right" value="1"/>
	   </attr>
   </declare-styleable>
</resources>

再到你目標的layout檔，加入xmlns:custom="http://schemas.android.com/apk/res/com.example.customviews"

格式為：http://schemas.android.com/apk/res/[your package name]

因為我的package是com.example.customviews，所以是http://schemas.android.com/apk/res/com.example.customviews

activity_main.xml
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<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
              xmlns:custom="http://schemas.android.com/apk/res/com.example.customviews">
	<com.example.customviews.charting.PieChart
	 custom:showText="true"
	 custom:labelPosition="left" />
</LinearLayout>

Apply Custom Attributes

PieChart.java
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package com.yume190.customviewtest;

import android.content.Context;
import android.content.res.TypedArray;
import android.util.AttributeSet;
import android.view.LayoutInflater;
import android.view.View;
import android.widget.LinearLayout;
import android.widget.TextView;

class PieChart extends LinearLayout {

    private String mShowText;
    private String mTextPos;

    public PieChart(Context context, AttributeSet attrs) {
        super(context, attrs);
        TypedArray a = context.getTheme().obtainStyledAttributes(attrs,R.styleable.PieChart,0, 0);

        try {
            mShowText = a.getString(R.styleable.PieChart_showText);
            mTextPos = a.getString(R.styleable.PieChart_labelPosition);
        } finally {
            a.recycle();
        }

        LayoutInflater.from(context).inflate(R.layout.piechart, this);

        TextView tv1 = (TextView)findViewById(R.id.textView1);
        TextView tv2 = (TextView)findViewById(R.id.textView2);

        tv1.setText(mShowText);
        tv2.setText(mTextPos);
    }
}

相關連結：

#Android #Custom_View