Develop Reference

An issue with layout params of relative layout

I am having an issue with my app, basically i have few layouts like this:
|ABC|
each letter describe one layout(A is the relative layout).
When i am adding an image view to the relative layout, this image view
can move over all the layout. But the relative layout became stretched to whole the width of the screen.
|A|
so basically you can`t see the B,C layouts any more.
This is my function:
public void startGame(){
int i;
for(i=0;i<currentLevelObs.size();i++){
if(currentLevelObs.get(i)==Globals.OBS_ENTRY_INDEX)
break;
}
lp = new RelativeLayout.LayoutParams(
RelativeLayout.LayoutParams.FILL_PARENT,
RelativeLayout.LayoutParams.FILL_PARENT);
lp.addRule(RelativeLayout.BELOW, (i+1));
lp.addRule(RelativeLayout.RIGHT_OF, i);
lp.leftMargin = 25;
ImageView img = new ImageView(this);
img.setLayoutParams(lp);
img.setBackgroundResource(R.drawable.hero);
gameLayout.addView(img);
}
This function called from onCreate method.

You have given layout width to fill parent. So it will take up the whole screen. Thats the problem. Change it to wrap-content and then check.

Add your ABC layouts to a ScrollView, that way you can scroll down to see B and C.
it should be like this:
<ScrollView
..
...
....>
<D
..>
A
B
C
</D>
</ScrollView>
a ScrollView can contain only 1 child, so keep your ABC in a D layout which is in ScrollView

RelativeLayout add rule "RelativeLayout.LEFT_OF" not working

I have a relativeLayout like below:
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="horizontal"
android:id="#+id/parent" >
<ListView
android:layout_width="360dp"
android:layout_height="600dp"
android:id="#+id/list"
android:inputType="text"
android:maxLines="1"
android:layout_margin="50dp"
android:layout_alignParentRight="true"
/>
</RelativeLayout>
In the java code, I want to add a view to the left of the listview, but it didn't worked:
m_relativeLayout = (RelativeLayout)findViewById(R.id.parent);
RelativeLayout.LayoutParams layoutParams = new RelativeLayout.LayoutParams(LayoutParams.WRAP_CONTENT,LayoutParams.WRAP_CONTENT);
layoutParams.addRule(RelativeLayout.LEFT_OF, m_listView.getId());
Button button2 = new Button(this);
button2.setText("I am button 2");
m_relativeLayout.addView(button2, layoutParams);
only if I set the listview to alignParentRight, it will work. Is this an android bug or I'm missing something?
I always try addView(View child, int index, LayoutParams params), but it might only work in the linearlayout. So is there an normal solution to make the RelativeLayout.LEFT_OF work?
EDIT
I have tried RelativeLayout.BELOW and RelativeLayout.RIGHT_OF, and they worked perfectly, so it means I don't have enough place to get the button? I tried to give more space, but it still not work.
I use Toshiba AT100 (1280*800) and landscape, so the space is enough. Test below and right just same as the left. I think If i put an control A in the relativelayout, then I add control B and decalare it's on the left of the control A, the result should be the control B will push the control A to its right, right?

I think If i put an control A in the relativelayout, then i add control B and declare it's on the left of the control A, the result should be the control B will push the control A to its right, right?
Your assumption is incorrect, the control A will not be pushed to the right unless you specified this with a RelativeLayout.LayoutParams rule. RelativeLayout places its children one one top of each other starting at the top-left corner of the screen if you don't specify placement rules for them. When you add the View A to the RelativeLayout without any rules(like layout_alignParentRight) it will be placed starting from the top-left corner of the screen. Then, when you add the View B, the rule to_leftOf will apply to this View position but this rule doesn't mean anything for the View A who will maintain its position on the screen. This will make View B to be place to the left of View A but outside of the screen as View A bounds start from the left border of the screen.
The Button will be placed to the left of the ListView when you use layout_alignParentRight="true" because there is now space to actually see the Button(it's not outside anymore). addView(View child, int index, LayoutParams params) works in a LinearLayout because the LinearLayout arranges its children in a row or column(depending on orientation) so when you add a View at a specific position, it will push the other Views after it to the right or below(depending on orientation)(there is no relative positioning of the views in a LinearLayout, the only rule is that the children come one after the other).
Starting with the ListView without any rules set on it, here is an example on how to make the Button to appear on the left of the ListView:
RelativeLayout.LayoutParams layoutParams = new RelativeLayout.LayoutParams(LayoutParams.WRAP_CONTENT,LayoutParams.WRAP_CONTENT);
Button button2 = new Button(this);
button2.setText("I am button 2");
button2.setId(1000);
m_relativeLayout.addView(button2, layoutParams);
RelativeLayout.LayoutParams rlp = (RelativeLayout.LayoutParams) m_listView
.getLayoutParams();
rlp.addRule(RelativeLayout.RIGHT_OF, button2.getId());
The Button will be added as normal to the screen and it will appear starting from the top-left corner of the screen. Without the two lines from the code above the Button and ListView will overlap as this is the normal behavior of RelativeLayout for children without any rules on them. We then explicitly modify the position of the ListView to move it to the right(with the last two line from the code above).

If your variable names are indicative, it's because you are adding the widget to a LinearLayout, so tags for a RelativeLayout get ignored.
This line is the one I'm talking about:
m_linearLayout.addView(button2, layoutParams);
EDIT
You say alignParentRight works... the only difference there is that ot doesn't take an anchor parameter. Perhaps m_listView.getId() isn't returning the proper id. You could step through with the debugger and see if it's returning a proper value.
Maybe you could try calling the id specifically...
layoutParams.addRule(RelativeLayout.LEFT_OF, R.id.list);

To perform it, use predefined view ID or declare one. In values folder create ids.xml then add a Item like this:
<item name="imageViewID" type="id"/>
use this id in your code where you are creating new Instance of view like this:
RelativeLayout layout=new RelativeLayout(context);
ImageView imageView = new ImageView(context);
imageView.setId(R.id.imageViewID);
RelativeLayout.LayoutParams layoutParams = new LayoutParams(50, 50);
layoutParams.addRule(RelativeLayout.CENTER_HORIZONTAL);
layout.addView(imageView, layoutParams);
TextView textView = new TextView(context);
RelativeLayout.LayoutParams textViewParams= new LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT);
textViewParams.addRule(RelativeLayout.CENTER_HORIZONTAL);
textViewParams.addRule(RelativeLayout.BELOW, imageView.getId());
layout.addView(nameView, nameLayoutParams);
or we can directly use this function View.generateViewId() to perform the same. Like this:
imageView.setId(View.generateViewId());

I think you might have forgotten to add m_listView to the RelativeLayout or m_listView's visibility would be GONE.
Can you please check for that?

setId before align is called, especially for the new object view.

If you are using a custom id and not a regular generated Android id (eg. R.id.my_id), make sure that the id is not equal to 0 (or negative), otherwise the rule will be ignored.

Why my edit text is not taking gravity...?

I am adding one edit text pro-grammatically, in that i am setting the gravity but its not reflecting.
code:
EditText bcc = new EditText(getApplicationContext());
LayoutParams para = new LayoutParams(LayoutParams.FILL_PARENT, 45);
//bcc.setBackgroundColor(Color.parseColor("#00000000"));
bcc.setTextColor(Color.parseColor("#000000"));
bcc.setSingleLine(true);
para.setMargins(0, 0, 0, 5); // left, top, right, bottom.
bcc.setTextSize(15);
bcc.setGravity(Gravity.BOTTOM);
bcc.setInputType(InputType.TYPE_TEXT_VARIATION_EMAIL_ADDRESS);
bcc.setId(100);
bcc.setLayoutParams(para);

This gravity bcc.setGravity(Gravity.BOTTOM); marks only how text should lay inside EditText.
If parent of EditText is RelativeLayout you can provide rules inside RelativeLayout.LayoutParams.

set gravity of parent of the view. If view parent is layout then the code will be like the following
((LinearLayout) bcc.getParent()).setGravity(Gravity.CENTER_VERTICAL);

Eventually you would be adding this EditText bcc to a view group? Depending on what type of ViewGroup the parent is, you would need to do the following:
LinearLayout:
via XML:
You have to set android:layout_gravity="center_vertical".
via code:
LinearLayout.LayoutParams lp = viewGroup.getLayoutParams();
lp.gravity = Gravity.CENTER_VERTICAL;
viewGroup.setLayoutParams(lp);
The code will be different for different parent layout types.

When you creating EditText programmatically, you must at first set setKeyListener(TextKeyListener.getInstance());
Otherwise your view will always be aligned with Gravity.TOP.
I don't know real reason, but before you specifiy any other parameter to EditText, you must set setKeyListener(TextKeyListener.getInstance());
Correction : It only work if you create you custom widget by extending EditText and defining your widget in XML. Only tested on Android 5.0.1

Add button to bottom of linear layout programmatically

I have a bunch of buttons displayed using the default gravity. The last button I add to the LinearLayout view is what I'd like to appear at the bottom of the view. How do I add it programmtically to appear at the bottom of the screen? I've tried setting the gravity, but everything falls to the bottom. I just want the one button to fall to the bottom of the screen. Ideally, I won't have to make another view.

Try this:
Button button = new Button(this);
youLinearLayout.addView(button, new LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT, Gravity.BOTTOM));
edit
sorry, the code above dont work.
You cant do this using an single LinearLayout if orientation==vertical.
You'll need create another layout(RelativeLayout) and add TextView to it.
RelativeLayout relative = new RelativeLayout(this);
RelativeLayout.LayoutParams params = new RelativeLayout.LayoutParams( LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT );
params.addRule(RelativeLayout.ALIGN_PARENT_BOTTOM);
relativeLayout.addView(textView, params);
linearLayout.addView(relativeLayout, new LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT));

If the rest of the screen is not empty, you can give android:layout_weight=0.0 to the Button, and 1.0 to the widget on the top.
In that way, widget with 1.0 weight will expand to fill empty areas, and Button with 0.0 will take only the default space, and being the last item addes to a vertical LinearLayout, it will be sticked to the bottom.

dynamically adding a view to activity layout

I have a custom view (an extension of a TextView) that I want to dynamically add to my Layout (don't want to include it in the main.xml file).
The book says to fetch the RelativeLayout using findViewById() in my java code then create a new instance of my custom view, then use addView on the RelativeLayout to add the new view.
I'm not getting any errors, but when I click my button to add the new view, nothing is happening (view isn't being added). Do I need to set additional properties on my custom view (layout width, layout height for example) in order for it to be shown?
EDIT: adding code
// changed to an imageview as I thought it might be easier to see an image
RelativeLayout rel = (RelativeLayout) findViewById(R.id.rellay);
MyCustomImageView mciv = new MyCustomImageView(null);
mciv.setId(5);
LayoutParams p = new LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT);
mciv.setLayoutParams(p);
mciv.setImageResource(R.drawable.someImage);
rel.Addview(mciv);

Please post your code where you add the view.
But yes, you might be missing the params for width and height. Try something like
LayoutParams p = new LayoutParams(LayoutParams.WRAP_CONTENT,LayoutParams.FILL_PARENT);
txtView.setLayoutParams(p);
or what you would like the width and height to be. Also in xml layout, layout_width and layout_height are required attributes.