I have found the android data binding with a custom view explanation, but this doesn't work for me because I do not understand this very well and also I have a little bit different case.
My idea:
I need canvas so I can draw something on it.
I have made a class(CustomView) that extends the View class. In CustomView class I have made instance of service that is in charge of drawing, and in the overridden onDraw
method I passed canvas to service class so the app can draw.
The problem:
In activity I have used setContentView(new CustomView());
, but this will not work if I want to use MVVM design pattern.
How can I separate these and make it to work with MVVM data binding?
I do not understand how and where to setup CustomView so it can be fetched/binded by view with data binding?
Please bear with me, I am new to android and do not have enough experience. Thanks :)
Ans: Simple answer would be yes you can ! But How? (Further explanation) ViewModelProviders required either context as Activity or Fragment . So you can retrieve context from your CustomView class using getContext() which would be Activity/Fragment where you're using it.
Model and ViewModel work together to get and save the data. View: The purpose of this layer is to inform the ViewModel about the user's action. This layer observes the ViewModel and does not contain any kind of application logic. ViewModel: It exposes those data streams which are relevant to the View.
DAO: DAO is a Data Access Object which is used for mapping SQL queries to functions.
The AndroidViewModel extends ViewModel , so it has all the same functionality. The only added functionality for AndroidViewModel is that it is context aware: when initializing AndroidViewModel you have to pass the Application context as a parameter.
I propose this solution:
Activity.java
package com.example.myapplication;
import android.databinding.DataBindingUtil;
import android.graphics.Color;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import com.example.myapplication.databinding.ActivityBinding;
import java.util.Arrays;
public class Activity extends AppCompatActivity
{
@Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
//Do magic with binding
ActivityBinding binding = DataBindingUtil.setContentView(this, R.layout.activity);
CustomViewModel viewModel = new CustomViewModel();
binding.setVariable(BR.vm, viewModel);
binding.executePendingBindings();
//Fill model
viewModel.backgroundFill.set(Color.WHITE);
viewModel.setCircleModels(Arrays.asList(new CircleModel(0, 0), new CircleModel(200, 400)));
}
}
CustomView.java
package com.example.myapplication;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.support.annotation.ColorInt;
import android.support.annotation.Nullable;
import android.util.AttributeSet;
import android.view.View;
import java.util.Collections;
import java.util.List;
public class CustomView extends View
{
private Paint mPaint = new Paint();
private int backgroundFill;
private List<CircleModel> circleModels = Collections.emptyList();
public CustomView(Context context, @Nullable AttributeSet attrs)
{
super(context, attrs);
mPaint.setStyle(Paint.Style.FILL);
}
@Override
protected void onDraw(Canvas canvas)
{
super.onDraw(canvas);
mPaint.setColor(backgroundFill);
canvas.drawPaint(mPaint);
mPaint.setColor(Color.BLUE);
for(CircleModel model : circleModels)
canvas.drawCircle(model.getX(), model.getY(), 100, mPaint);
}
public void setBackgroundFill(@ColorInt int backgroundFill)
{
this.backgroundFill = backgroundFill;
}
public void setCircles(List<CircleModel> circles)
{
circleModels = circles;
}
}
CustomViewModel.java
package com.example.myapplication;
import android.databinding.BaseObservable;
import android.databinding.Bindable;
import android.databinding.ObservableInt;
import java.util.ArrayList;
import java.util.List;
public class CustomViewModel extends BaseObservable
{
public final ObservableInt backgroundFill = new ObservableInt();
@Bindable
private List<CircleModel> circleModels = new ArrayList<>();
public List<CircleModel> getCircleModels()
{
return circleModels;
}
public void setCircleModels(List<CircleModel> circleModels)
{
this.circleModels = circleModels;
notifyPropertyChanged(BR.circleModels);
}
}
CircleModel.java
public class CircleModel
{
private int x;
private int y;
public CircleModel(int x, int y)
{
this.x = x;
this.y = y;
}
public int getX() { return x; }
public int getY() { return y; }
}
activity.xml
<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto">
<data>
<variable
name="vm"
type="com.example.myapplication.CustomViewModel" />
</data>
<android.support.design.widget.CoordinatorLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
<com.example.myapplication.CustomView
android:id="@+id/canvas"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:backgroundFill="@{vm.backgroundFill}"
app:circles="@{vm.circleModels}"/>
<!--Setters in CustomView-->
<!--app:backgroundFill="@{vm.backgroundFill}"-->
<!--app:circles="@{vm.circleModels}"-->
</android.support.design.widget.CoordinatorLayout>
</layout>
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