我的约束布局:
<?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/main"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<Button
android:id="@+id/btn"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="0dp"
android:layout_marginTop="0dp"
android:layout_marginEnd="0dp"
android:layout_marginBottom="0dp"
android:minWidth="0dp"
android:minHeight="0dp"
android:text="@string/start"
android:visibility="visible"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
</android.support.constraint.ConstraintLayout>
我的简化代码:
import android.annotation.SuppressLint;
import android.os.Handler;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.DisplayMetrics;
import android.view.MotionEvent;
import android.view.View;
import android.widget.Button;
import java.util.Random;
public class MainActivity extends AppCompatActivity {
final Random rand = new Random();
private Button btn;
private float widthPixels, heightPixels;
private float minBtnSize, maxBtnSize;
@SuppressLint("ClickableViewAccessibility")
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
/* Obtaining screen's display properties. */
final DisplayMetrics displaymetrics = new DisplayMetrics();
getWindowManager().getDefaultDisplay().getMetrics(displaymetrics);
widthPixels = displaymetrics.widthPixels;
heightPixels = displaymetrics.heightPixels; // includes BotNavBar
heightPixels -= 162; // size of the "Virtual Nav Bar" at the bottom
float minDim = Math.min(widthPixels, heightPixels);
minBtnSize = minDim/25;
maxBtnSize = minDim/2;
/* Setting up the experiment's Button*/
btn = findViewById(R.id.btn);
btn.setOnTouchListener(new View.OnTouchListener(){
public boolean onTouch(View view, MotionEvent event){
/* Touch Events. */
switch (event.getAction()) {
case MotionEvent.ACTION_UP:
/* Move and resize the button. */
launchNewAttempt(x, y);
break;
default:
break;
}
return true;
}
});
/* Setting up the beginning Button's state. */
init();
}
/**
* Initializing the Button shown at the very beginning.
*/
private void init() {
btn.setX(0);
btn.setY(0);
btn.setWidth((int)widthPixels);
btn.setHeight((int)heightPixels);
}
/**
* Called whenever the user releases the experiment's button (pressed "UP").
*/
private void launchNewAttempt() {
/* Random size for the "new" button. */
int size=(int)(minBtnSize+(maxBtnSize-minBtnSize)*rand.nextDouble());
btn.setWidth(size);
btn.setHeight(size);
/* Random position for the "new" button. */
float dx = rand.nextFloat() * (widthPixels - size);
float dy = rand.nextFloat() * (heightPixels - size);
btn.setX(dx);
btn.setY(dy);
}
}
预期行为:
填充整个屏幕的按钮出现在开头.按下后,相同的按钮被调整大小(正方形,边长至少为屏幕宽度的1/25,最多为屏幕宽度的1/2),并在屏幕上随机移动.每次用户再次按下该按钮时,其行为方式相同(新的随机位置和大小).
我的问题:
btn.setX()和btn.setY()似乎没有按预期运行.我原以为他们会在屏幕上确定按钮的绝对位置,但是对于init()使用以下示例代码有一个奇怪的行为:
btn.setX(0);
btn.setY(0);
btn.setWidth(150);
btn.setHeight(150);
大小似乎没问题,但位置似乎是相对于屏幕中间的(虽然它似乎也取决于按钮的大小,因为使用前面介绍的代码它正确填充整个屏幕).我希望这个位置相对于屏幕的左上角(不包括顶部的ActionBar / TitleBar,也不包括底部的NavigationBar).
当我运行当前代码时,按钮实际上有时会在屏幕外关闭.这有什么不对?
最佳答案 我尝试用LinearLayout替换布局的根节点代码并且它正常工作,这意味着问题与ContraintLayout的内部逻辑有关.知道我试图改变按钮的位置,考虑约束而不是绝对位置,特别是关于按钮的顶部和起始边距.因此,launchNewAttempt()方法可以类似于:
private void launchNewAttempt() {
final int size = (int) (minBtnSize + (maxBtnSize - minBtnSize) * rand.nextDouble());
final int left = (int) (rand.nextFloat() * (widthPixels - size));
final int top = (int) (rand.nextFloat() * (heightPixels - size));
final ConstraintLayout.LayoutParams layoutParams = (ConstraintLayout.LayoutParams) btn.getLayoutParams();
layoutParams.width = size;
layoutParams.height = size;
layoutParams.leftMargin = left;
layoutParams.topMargin = top;
btn.setLayoutParams(layoutParams);
}
我还只保留了两个约束,将按钮放在布局中,并删除了底部和底部的按钮:
<Button
android:id="@+id/btn"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="0dp"
android:layout_marginTop="0dp"
android:layout_marginEnd="0dp"
android:layout_marginBottom="0dp"
android:minWidth="0dp"
android:minHeight="0dp"
android:text="Start"
android:visibility="visible"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
希望这对你有用.