如何为同一 ConstraintLayout 中的不同 TextView 使用单独的 ConstraintSet 操作？答案

【问题标题】：How to utilise seperate ConstraintSet actions for different TextViews in the same ConstraintLayout?如何为同一 ConstraintLayout 中的不同 TextView 使用单独的 ConstraintSet 操作？
【发布时间】：2018-06-30 01:50:43
【问题描述】：

我的问题来自这个问题：Android : How to programatically set layout_constraintRight_toRightOf "parent"。

我编写了以下代码，应该将新的 TextView 限制在 ConstraintLayout 的左侧 (btnSendL) 或右侧 (btnSendR)。

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

    final ConstraintLayout clMessagesContainer = (ConstraintLayout) findViewById(R.id.clMessagesContainer);
    final EditText txtMessage = (EditText) findViewById(R.id.txtMessage);
    Button btnSendL = (Button) findViewById(R.id.btnSendL);
    Button btnSendR = (Button) findViewById(R.id.btnSendR);

    btnSendL.setOnClickListener(new View.OnClickListener(){
        @Override
        public void onClick(View v) {

            TextView lblNxtMessage = new TextView(MainActivity.this);
            lblNxtMessage.setLayoutParams(new ConstraintLayout.LayoutParams(
                    ConstraintLayout.LayoutParams.WRAP_CONTENT,
                    ConstraintLayout.LayoutParams.WRAP_CONTENT));

            lblNxtMessage.setText(txtMessage.getText().toString());
            clMessagesContainer.addView(lblNxtMessage);

            ConstraintSet csL = new ConstraintSet();
            csL.clone(clMessagesContainer);
            csL.connect(lblNxtMessage.getId(), ConstraintSet.LEFT, ConstraintSet.PARENT_ID, ConstraintSet.LEFT, 0);
            csL.connect(lblNxtMessage.getId(), ConstraintSet.TOP, ConstraintSet.PARENT_ID, ConstraintSet.TOP, 0);
            csL.applyTo(clMessagesContainer);

        }
    });

    btnSendR.setOnClickListener(new View.OnClickListener(){
        @Override
        public void onClick(View v) {

            TextView lblNxtMessage = new TextView(MainActivity.this);
            lblNxtMessage.setLayoutParams(new ConstraintLayout.LayoutParams(
                    ConstraintLayout.LayoutParams.WRAP_CONTENT,
                    ConstraintLayout.LayoutParams.WRAP_CONTENT));

            lblNxtMessage.setText(txtMessage.getText().toString());
            clMessagesContainer.addView(lblNxtMessage);

            ConstraintSet csR = new ConstraintSet();
            csR.clone(clMessagesContainer);
            csR.connect(lblNxtMessage.getId(), ConstraintSet.RIGHT, ConstraintSet.PARENT_ID, ConstraintSet.RIGHT, 0);
            csR.connect(lblNxtMessage.getId(), ConstraintSet.TOP, ConstraintSet.PARENT_ID, ConstraintSet.TOP, 0);
            csR.applyTo(clMessagesContainer);
        }
    });


}

但是，每次单击其中一个时，都会对已创建的所有 TextView 执行此操作，而不仅仅是在最近的 onClickListenerMethod 中创建的 TextView。我该如何解决这个问题？

【问题讨论】：

标签： android android-layout android-studio

【解决方案1】：

发生这种情况是因为每个新创建的 View 都有一个默认的 ID -1，因此应用于其中任何一个的约束都会影响带有 ID 的所有 Views。

要解决此问题，您需要为每个创建的View 生成一个唯一的ID。最简单的方法是使用View 类中的静态方法generateViewId()。用法如下所示：

TextView lblNxtMessage = new TextView(MainActivity.this);
lblNxtMessage.setId(View.generateViewId());

【讨论】：

【解决方案2】：

我向新的TextView推荐setId()

lblNxtMessage.setId(View.generateViewId());

示例

 public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(final Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        final ConstraintLayout clMessagesContainer = (ConstraintLayout) findViewById(R.id.clMessagesContainer);
        final EditText txtMessage = (EditText) findViewById(R.id.txtMessage);
        Button btnSendL = (Button) findViewById(R.id.btnSendL);
        Button btnSendR = (Button) findViewById(R.id.btnSendR);

        btnSendL.setOnClickListener(new View.OnClickListener(){
            @Override
            public void onClick(View v) {

                TextView lblNxtMessage = new TextView(MainActivity.this);
                lblNxtMessage.setId(View.generateViewId());
                lblNxtMessage.setLayoutParams(new ConstraintLayout.LayoutParams(
                        ConstraintLayout.LayoutParams.WRAP_CONTENT,
                        ConstraintLayout.LayoutParams.WRAP_CONTENT));

                lblNxtMessage.setText(txtMessage.getText().toString());
                clMessagesContainer.addView(lblNxtMessage);

                ConstraintSet csL = new ConstraintSet();
                csL.clone(clMessagesContainer);
                csL.connect(lblNxtMessage.getId(), ConstraintSet.LEFT, ConstraintSet.PARENT_ID, ConstraintSet.LEFT, 0);
                csL.connect(lblNxtMessage.getId(), ConstraintSet.TOP, ConstraintSet.PARENT_ID, ConstraintSet.TOP, 0);
                csL.applyTo(clMessagesContainer);

            }
        });

        btnSendR.setOnClickListener(new View.OnClickListener(){
            @Override
            public void onClick(View v) {

                TextView lblNxtMessage = new TextView(MainActivity.this);
                lblNxtMessage.setId(View.generateViewId());
                lblNxtMessage.setLayoutParams(new ConstraintLayout.LayoutParams(
                        ConstraintLayout.LayoutParams.WRAP_CONTENT,
                        ConstraintLayout.LayoutParams.WRAP_CONTENT));

                lblNxtMessage.setText(txtMessage.getText().toString());
                clMessagesContainer.addView(lblNxtMessage);

                ConstraintSet csR = new ConstraintSet();
                csR.clone(clMessagesContainer);
                csR.connect(lblNxtMessage.getId(), ConstraintSet.RIGHT, ConstraintSet.PARENT_ID, ConstraintSet.RIGHT, 0);
                csR.connect(lblNxtMessage.getId(), ConstraintSet.TOP, ConstraintSet.PARENT_ID, ConstraintSet.TOP, 0);
                csR.applyTo(clMessagesContainer);
            }
        });
    }
}

【讨论】：