How to utilise seperate ConstraintSet actions for different TextViews in the same ConstraintLayout?

My question follows on from this question: Android : How to programatically set layout_constraintRight_toRightOf "parent".

I have the written the following code that should constrain the new TextView to either the left (btnSendL) or the right (btnSendR) of a ConstraintLayout.

@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);
}
});


}


However, each time I click either, this is done so for all TextViews already created, instead of only the TextView created inside the most recent onClickListenerMethod. How can I fix this?

2 Answers
2

This happens because each newly created View has a default ID of -1, so constraints applied to any of them affect all Views with that ID.

View

ID

-1

Views

ID

To fix this, you need to generate a unique ID for every created View. The simplest way is to use a static method generateViewId() from the View class. The usage would look like this:

ID

View

generateViewId()

View

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


I recommend setId() to new TextView

setId()

TextView

lblNxtMessage.setId(View.generateViewId());


EXAMPLE

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);
}
});
}
}


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