Question

我可以使用ConstraintSet以编程方式修改ConstraintLayout中视图的约束，但在应用修改之前，我想测试它尚未完成。为此，我需要以编程方式访问ConstraintLayout中视图的当前约束。

例如，在这里，我想删除TextView“title”顶部和TextView视图“subtitle”底部之间的约束。然后将TextView'title'的顶部限制在'videoView'的底部。但首先我需要检查TextView'标题'是否已经被限制在'videoView'的底部（从android's official website修改的代码）。注意，我不能在这个网站上插入最后一行HTML，它是尖括号中的/android.support.constraint.ConstraintLayout。

vec4 EncodeExp( in float value )
{
    int exponent  = int( log2( abs( value ) ) + 1.0 );
    value        /= exp2( float( exponent ) );
    value         = (value + 1.0) * (256.0*256.0*256.0 - 1.0) / (2.0*256.0*256.0*256.0);
    vec4 encode   = fract( value * vec4(1.0, 256.0, 256.0*256.0, 256.0*256.0*256.0) );
    return vec4( encode.xyz - encode.yzw / 256.0 + 1.0/512.0, (float(exponent) + 127.5) / 256.0 );
}

float DecodeExp( in vec4 pack )
{
    int exponent = int( pack.w * 256.0 - 127.0 );
    float value  = dot( pack.xyz, 1.0 / vec3(1.0, 256.0, 256.0*256.0) );
    value        = value * (2.0*256.0*256.0*256.0) / (256.0*256.0*256.0 - 1.0) - 1.0;
    return value * exp2( float(exponent) );
}

}

public class MainActivity extends AppCompatActivity {
ConstraintSet mConstraintSet = new ConstraintSet(); // create a Constraint Set
ConstraintLayout mConstraintLayout; // cache the ConstraintLayout

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    mConstraintLayout = (ConstraintLayout) findViewById(R.id.root);
    mConstraintSet.clone(mConstraintLayout); // get constraints from ConstraintSet
}

public void userDoesSomething(View v) {
    //test if title has already been constrained to bottom of videoView
    if (mConstraintLayout 'TITLE' IS NOT CONSTRAINED TO THE BOTTOM OF 'VIDEOVIEW'){
        mConstraintSet.connect(R.id.Title, ConstraintSet.TOP, R.id.videoView, ConstraintSet.BOTTOM); // set new constraints to ConstraintSet
        mConstraintSet.applyTo(mConstraintLayout); // set new constraints to ConstraintLayout
    }
}

Answer 1

对我的承认，没有办法，你可以试着比较两个ConstraintLayout.LayoutParams，例如：

public class MainActivity extends AppCompatActivity {
ConstraintSet mConstraintSet = new ConstraintSet(); // create a Constraint Set
ConstraintLayout mConstraintLayout; // cache the ConstraintLayout

int mConstraintValue;
TextView mTextView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mConstraintLayout = (ConstraintLayout) findViewById(R.id.root);
        mTextView = (TextView) findViewById(R.id.title);
        mConstraintSet.clone(mConstraintLayout); // get constraints from ConstraintSet
        ConstraintLayout.LayoutParams params = (ConstraintLayout.LayoutParams) mTextView.getLayoutParams();
        mConstraintValue = params.topToBottom;
    }

    public void userDoesSomething(View v) {
        //test if title has already been constrained to bottom of videoView
         ConstraintLayout.LayoutParams params = (ConstraintLayout.LayoutParams) mTextView.getLayoutParams();
        if (mConstraintValue.equals(params.topToBottom)){
            mConstraintSet.connect(R.id.Title, ConstraintSet.TOP, R.id.videoView, ConstraintSet.BOTTOM); // set new constraints to ConstraintSet
            mConstraintSet.applyTo(mConstraintLayout); // set new constraints to ConstraintLayout
        }
    }
}

希望这有帮助。

如何以编程方式访问ConstraintLayout中的当前视图约束？

1 个答案: