我正在尝试扩展 ConstraintLayout 功能，使 ProgressBar 具有全屏半透明背景色。我的想法是我可以重复使用此布局并调用 hideLoading() 和 showLoading()。进度条必须居中。

问题是:当调用 constraintSet.applyTo(this) 时，所有具有 ConstraintSet.connect(...) 的 View 都被调用消失了，或者没有画出来。由于对它们的所有操作都将被忽略，它们根本不会显示在屏幕上。

这是我的:

public class ConstraintLayout extends android.support.constraint.ConstraintLayout {

    private View background;
    private ProgressBar progressBar;

    public ConstraintLayout(Context context) {
        super(context);
        addLoader();
    }

    public ConstraintLayout(Context context, AttributeSet attrs) {
        super(context, attrs);
        addLoader();
    }

    public ConstraintLayout(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        addLoader();
    }

    private void addLoader(){
        int wrapContent = LayoutParams.WRAP_CONTENT;
        int matchParent = LayoutParams.MATCH_PARENT;

        ConstraintSet constraintSet = new ConstraintSet();
        constraintSet.clone(this);

        background = new View(getContext());
        background.setBackgroundColor(getResources()
                .getColor(R.color.background_loader_color));
        background.setId(generateViewId());
        addView(background, new ConstraintLayout.LayoutParams(matchParent, matchParent));

        constraintSet.connect(background.getId(), ConstraintSet.TOP, 
                ConstraintSet.PARENT_ID, ConstraintSet.TOP, 0);
        constraintSet.connect(background.getId(), ConstraintSet.BOTTOM, 
                ConstraintSet.PARENT_ID, ConstraintSet.BOTTOM, 0);
        constraintSet.connect(background.getId(), ConstraintSet.LEFT, 
                ConstraintSet.PARENT_ID, ConstraintSet.LEFT, 0);
        constraintSet.connect(background.getId(), ConstraintSet.RIGHT, 
                ConstraintSet.PARENT_ID, ConstraintSet.RIGHT, 0);

        progressBar = new ProgressBar(getContext(), null, android.R.attr.progressBarStyleLarge);
        progressBar.setId(generateViewId());
        addView(progressBar, new ConstraintLayout.LayoutParams(wrapContent, wrapContent));

        constraintSet.connect(progressBar.getId(), ConstraintSet.TOP, 
                ConstraintSet.PARENT_ID, ConstraintSet.TOP, 0);
        constraintSet.connect(progressBar.getId(), ConstraintSet.BOTTOM, 
                ConstraintSet.PARENT_ID, ConstraintSet.BOTTOM, 0);
        constraintSet.connect(progressBar.getId(), ConstraintSet.START, 
                ConstraintSet.PARENT_ID, ConstraintSet.START, 0);
        constraintSet.connect(progressBar.getId(), ConstraintSet.END, 
                ConstraintSet.PARENT_ID, ConstraintSet.END, 0);

        constraintSet.applyTo(this);
    }

    public void showLoading(){
        background.setVisibility(VISIBLE);
        progressBar.setVisibility(VISIBLE);
    }

    public void hideLoading(){
        background.setVisibility(GONE);
        progressBar.setVisibility(GONE);
    }
}

这是我的 和我想要的

最佳答案

问题似乎是您将背景约束设置为 MATCH_PARENT，这在 ConstraintLayouts 中是无效的。我假设您的意思是 LayoutParams.MATCH_CONSTRAINT。

我假设您希望您的布局“模拟”此 XML:

<?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"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <View
        android:id="@+id/bkg"
        android:layout_width="0dp"
        android:layout_height="0dp"
        android:background="@android:color/holo_red_dark"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <ProgressBar
        android:id="@+id/progress_bar"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />
</android.support.constraint.ConstraintLayout>

看起来像:

tl;dr:将行 int matchParent = LayoutParams.MATCH_PARENT; 更改为 int matchParent = LayoutParams.MATCH_CONSTRAINT;

更新:我尝试了自己的解决方案但没有奏效，所以我花了几分钟查看您的代码并找到了问题所在。我正在使用 ConstraintLayout 1.1.0

1. 是的，使用 MATCH CONSTRAINT。
2. 您正在为尚不存在的 View 设置约束……所以我重新创建了您的“自定义布局”，这是我的:

Main Activity 只是通过 setContentView(R.layout.demo_layout)

<?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"
                                             android:id="@+id/root"
                                             android:layout_width="match_parent"
                                             android:layout_height="match_parent"
                                             tools:context=".MainActivity"
    >
    <com.so.ProgressConstraintLayout
        android:id="@+id/demo_progress_container"
        android:layout_width="0dp"
        android:layout_height="0dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        />
</android.support.constraint.ConstraintLayout>

还有我的 ProgressConstraintLayout……我从你那里复制并修改了它:

package com.so;

import android.content.Context;
import android.support.constraint.ConstraintLayout;
import android.support.constraint.ConstraintSet;
import android.util.AttributeSet;
import android.view.View;
import android.widget.ProgressBar;

public class ProgressConstraintLayout extends ConstraintLayout {

    private View background;
    private ProgressBar progressBar;

    public ProgressConstraintLayout(Context context) {
        super(context);
        addLoader();
    }

    public ProgressConstraintLayout(Context context, AttributeSet attrs) {
        super(context, attrs);
        addLoader();
    }

    public ProgressConstraintLayout(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        addLoader();
    }

    private void addLoader() {
        int wrapContent = LayoutParams.WRAP_CONTENT;
        int matchConstraint = LayoutParams.MATCH_CONSTRAINT;

        ConstraintSet constraintSet = new ConstraintSet();

        background = new View(getContext());
        background.setBackgroundColor(getResources().getColor(android.R.color.holo_blue_bright, getContext().getTheme()));
        background.setId(generateViewId());
        addView(background, new ConstraintLayout.LayoutParams(matchConstraint, matchConstraint));

        progressBar = new ProgressBar(getContext(), null, android.R.attr.progressBarStyleLarge);
        progressBar.setIndeterminate(true);
        progressBar.setId(generateViewId());
        addView(progressBar, new ConstraintLayout.LayoutParams(wrapContent, wrapContent));

        constraintSet.clone(this);
        constraintSet.connect(background.getId(), ConstraintSet.TOP, ConstraintSet.PARENT_ID, ConstraintSet.TOP);
        constraintSet.connect(background.getId(), ConstraintSet.BOTTOM, ConstraintSet.PARENT_ID, ConstraintSet.BOTTOM);
        constraintSet.connect(background.getId(), ConstraintSet.START, ConstraintSet.PARENT_ID, ConstraintSet.START);
        constraintSet.connect(background.getId(), ConstraintSet.END, ConstraintSet.PARENT_ID, ConstraintSet.END);
        constraintSet.connect(progressBar.getId(), ConstraintSet.TOP, ConstraintSet.PARENT_ID, ConstraintSet.TOP);
        constraintSet.connect(progressBar.getId(), ConstraintSet.BOTTOM, ConstraintSet.PARENT_ID, ConstraintSet.BOTTOM);
        constraintSet.connect(progressBar.getId(), ConstraintSet.START, ConstraintSet.PARENT_ID, ConstraintSet.START);
        constraintSet.connect(progressBar.getId(), ConstraintSet.END, ConstraintSet.PARENT_ID, ConstraintSet.END);
        constraintSet.applyTo(this);
    }

    public void showLoading() {
        background.setVisibility(VISIBLE);
        progressBar.setVisibility(VISIBLE);
    }

    public void hideLoading() {
        background.setVisibility(GONE);
        progressBar.setVisibility(GONE);
    }
}

如果您想知道它的外观……很无聊，但我有什么资格评判:

关于android - ConstraintSet.applyTo 时 View 消失，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/50117404/