開發中經常遇到一些使用率很高的組合控件,比如用戶頭像、名稱、背景及點擊動畫,再比如新聞列表中的新聞圖片、標題、時間、評論等,這些都可以“抽象”成一個組合式控件,以便於調用。
這裏以一個簡要的新聞版塊信息爲例,簡要說明一下組合控件的構建流程。效果圖:
1、在attrs.xml中定義屬性,供自定義類InfoBlockView使用:
<?xml version="1.0" encoding="utf-8"?>
<resources>
<declare-styleable name="InfoBlockView">
<attr name="img" format="reference"/>
<attr name="title" format="string"/>
<attr name="author" format="string"/>
<attr name="comment" format="string"/>
</declare-styleable>
</resources>
2、定義佈局info_block_layout.xml,至於佈局中的控件、間距可以內部設定,也可以通過設置屬性值,在控件外部控制:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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:layout_margin="20dp"
android:orientation="vertical">
<TextView
android:id="@+id/block_title"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:textSize="18sp"
android:textColor="@android:color/black"
android:text="xxx"/>
<ImageView
android:id="@+id/block_image_view"
android:layout_width="match_parent"
android:layout_height="150dp"
android:scaleType="fitXY"
tools:srcCompat="@tools:sample/backgrounds/scenic[1]" />
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal">
<TextView
android:id="@+id/block_author"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="作者"/>
<TextView
android:id="@+id/block_comment"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="20dp"
android:text="評論數"/>
</LinearLayout>
</LinearLayout>
3、定義類InfoBlockView,這個佈局中使用的是LinearLayout,因此自定義類繼承了LinearLayout。
注意代碼中引用自定義屬性的格式:R.styleable.[自定義名]_[屬性名]。
package com.example.blc.myviewapplication;
import android.content.Context;
import android.content.res.TypedArray;
import android.support.annotation.Nullable;
import android.util.AttributeSet;
import android.view.LayoutInflater;
import android.widget.ImageView;
import android.widget.LinearLayout;
import android.widget.TextView;
public class InfoBlockView extends LinearLayout {
public InfoBlockView(Context context) {
super(context);
init(context, null);
}
public InfoBlockView(Context context, @Nullable AttributeSet attrs) {
super(context, attrs);
init(context, attrs);
}
public InfoBlockView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
init(context, attrs);
}
void init(Context context, @Nullable AttributeSet attrs){
//加載自定義佈局
LayoutInflater.from(context).inflate(R.layout.info_block_layout, this, true);
if (attrs != null){
TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.InfoBlockView);
//獲取自定義屬性,填充佈局中的控件
//填充圖片
int img = a.getResourceId(R.styleable.InfoBlockView_img, 0);
ImageView imgView = findViewById(R.id.block_image_view);
imgView.setImageResource(img);
//填充作者
String author = a.getString(R.styleable.InfoBlockView_author);
TextView authorText = findViewById(R.id.block_author);
authorText.setText(author);
//填充標題
String title = a.getString(R.styleable.InfoBlockView_title);
TextView titleText = findViewById(R.id.block_title);
titleText.setText(title);
//填充評論數
String comment = a.getString(R.styleable.InfoBlockView_comment);
TextView commentText = findViewById(R.id.block_comment);
commentText.setText(comment);
a.recycle();
}
}
}
4、在需要使用這個控件的佈局中引用該控件,這裏在一個ScrollView的線性佈局中加入幾個上面自定義好的控件:
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
xmlns:test="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<ScrollView
android:layout_width="match_parent"
android:layout_height="match_parent">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:showDividers="middle"
android:dividerPadding="20dp"
android:divider="@android:drawable/divider_horizontal_bright"
android:orientation="vertical">
<com.example.blc.myviewapplication.InfoBlockView
android:layout_width="match_parent"
android:layout_height="wrap_content"
test:img="@drawable/img1"
test:title="@string/title2"
test:comment="@string/comment2"
test:author="@string/author2">
</com.example.blc.myviewapplication.InfoBlockView>
<com.example.blc.myviewapplication.InfoBlockView
android:layout_width="match_parent"
android:layout_height="wrap_content"
test:img="@drawable/img2"
test:title="@string/title3"
test:comment="@string/comment3"
test:author="@string/author3">
</com.example.blc.myviewapplication.InfoBlockView>
</LinearLayout>
</ScrollView>
</android.support.constraint.ConstraintLayout>
5、在strings.xml中定義了幾個字符串:
<resources>
<string name="app_name">MyViewApplication</string>
<string name="title1">現在是讀書時間!</string>
<string name="title2">這個草莓有點紅!</string>
<string name="title3">說實話,我有點渴了!</string>
<string name="author1">小紅</string>
<string name="author2">小白</string>
<string name="author3">小LAN</string>
<string name="comment1">2評論</string>
<string name="comment2">10評論</string>
<string name="comment3">0評論</string>
</resources>
OK!粗略的效果圖(還望包涵~):