android - 在 ConstraintLayout 中向 View 添加约束会忽略左右边距

Question

我想在 java 中向 ConstraintLayout 添加一些 View 。这是布局 xml:

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout 
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/constraint_layout"
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
</android.support.constraint.ConstraintLayout>

这是 Activity 的代码:

public class MainActivity extends AppCompatActivity {

    private ConstraintLayout layout;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        layout = (ConstraintLayout) findViewById(R.id.constraint_layout);
        TextView textView = new TextView(this);
        textView.setId(View.generateViewId());
        textView.setBackgroundColor(Color.RED);
        textView.setText("ciao");
        layout.addView(textView);

        ConstraintSet constraints = new ConstraintSet();
        constraints.clone(layout);
        constraints.constrainWidth(textView.getId(), ConstraintSet.MATCH_CONSTRAINT);
        constraints.constrainHeight(textView.getId(), ConstraintSet.MATCH_CONSTRAINT);
        constraints.setDimensionRatio(textView.getId(), "h,1:1");
        constraints.connect(textView.getId(), ConstraintSet.LEFT, ConstraintSet.PARENT_ID, ConstraintSet.LEFT, 8);
        constraints.connect(textView.getId(), ConstraintSet.RIGHT, ConstraintSet.PARENT_ID, ConstraintSet.RIGHT, 8);
        constraints.connect(textView.getId(), ConstraintSet.TOP, ConstraintSet.PARENT_ID, ConstraintSet.TOP, 8);
        constraints.applyTo(layout);
    }
}

左右约束边距(请参阅连接调用)被简单地忽略。我正在使用 25 版的 sdk。 这是一个错误吗？或者我做错了什么？ The TextView without left and right margin

Answer 1

按照您指定的方式设置左右边距绝对有效。为什么它不对我来说仍然是个谜。作为变通方法，您可以在 TextView 上显式设置边距，如下所示:

ConstraintLayout.LayoutParams params =
        new ConstraintLayout.LayoutParams(ConstraintLayout.LayoutParams.MATCH_CONSTRAINT,
        ConstraintLayout.LayoutParams.MATCH_CONSTRAINT);
params.setMargins(8,8,8,8);
textView.setLayoutParams(params);