Introduction
After the writing of your first application and the first tests. It is time to make our application a bit more testable by using dependency injection. I choose to use RoboGuice for this, which is a subproject of Guice made especially for the Android sub-culture.
Setting it up.
You can read how to set up Roboguice to work with your application on the wiki. It’s not rocket science.
I ended up with using Roboguice 1.1.2 and the guice-2.0-no_aop.jar for this little demonstration.
I ran into a little problem with the myApplication part because they don’t mention the imports you need for this to work and Eclipse did not seem to know where to look for them. So here it is.
package be.baes;
import java.util.List;
import roboguice.application.RoboApplication;
import com.google.inject.*;
public class MyApplication extends RoboApplication
{
protected void addApplicationModules(List<Module> modules)
{
modules.add(new MyModule());
}
}
The project
This little project is simple. Just add a tabcontrol with 3 tabs and a textview in each tab.
So here is the main.xml.
<?xml version="1.0" encoding="utf-8"?>
<TabHost xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@android:id/tabhost"
android:layout_width="match_parent"
android:layout_height="match_parent">
<LinearLayout
android:id="@+id/linearLayout1"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<TabWidget
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="@android:id/tabs">
</TabWidget>
<FrameLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="@android:id/tabcontent">
<TextView
android:layout_width="fill_parent"
android:id="@+id/textView1"
android:layout_height="fill_parent"
android:text="This is the first tab">
</TextView>
<TextView
android:layout_width="fill_parent"
android:id="@+id/textView2"
android:layout_height="fill_parent"
android:text="This is the second tab">
</TextView>
<TextView
android:layout_width="fill_parent"
android:id="@+id/textView3"
android:layout_height="fill_parent"
android:text="This is the third tab">
</TextView>
</FrameLayout>
</LinearLayout>
</TabHost>
and here is the Activity before the Roboguicing.
```java package be.baes;
import android.app.TabActivity; import android.content.res.Resources; import android.os.Bundle; import android.util.Log; import android.widget.TabHost;
public class TabViewActivity extends TabActivity { TabHost tabHost; Resources res;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
res = getResources();
tabHost= this.getTabHost();
tabHost.addTab(tabHost
.newTabSpec("tab_test1")
.setIndicator("TAB 1", res.getDrawable(R.drawable.tab_one))
.setContent(R.id.editText1));
tabHost.addTab(tabHost
.newTabSpec("tab_test2")
.setIndicator("TAB 2", res.getDrawable(R.drawable.tab_one))
.setContent(R.id.editText2));
tabHost.addTab(tabHost
.newTabSpec("tab_test3")
.setIndicator("TAB 3", res.getDrawable(R.drawable.tab_one))
.setContent(R.id.editText3));
tabHost.setCurrentTab(0);
TabHost.OnTabChangeListener tabChangeListener = new TabHost.OnTabChangeListener()
{
@Override
public void onTabChanged(String arg0) {
Log.d("cbaes", "Tab was changed with arg" + arg0);
}
};
tabHost.setOnTabChangedListener(tabChangeListener);
}
}``` That looks ugly. So let’s use some DI to remove some of that code.
Injecting views and resources
First I’m going to inject some views and resources because that’s something Roboguice does very well.
```java package be.baes;
import roboguice.activity.*; import roboguice.inject.InjectResource; import roboguice.inject.InjectView; import android.graphics.drawable.Drawable; import android.os.Bundle; import android.util.Log; import android.widget.TabHost; import android.widget.TextView;
public class TabViewActivity extends RoboTabActivity { @InjectResource(R.drawable.tab_one) Drawable tab_one_res; @InjectView(R.id.textView1) TextView textView1; @InjectView(R.id.textView2) TextView textView2; @InjectView(R.id.textView3) TextView textView3;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
TabHost tabHost= this.getTabHost();
addTab(tabHost,"tab_test1","TAB 1",tab_one_res,textView1.getId());
addTab(tabHost,"tab_test2","TAB 2",tab_one_res,textView2.getId());
addTab(tabHost,"tab_test3","TAB 3",tab_one_res,textView3.getId());
tabHost.setCurrentTab(0);
TabHost.OnTabChangeListener tabChangeListener = new TabHost.OnTabChangeListener()
{
@Override
public void onTabChanged(String arg0) {
Log.d("cbaes", "Tab was changed with arg" + arg0);
}
};
tabHost.setOnTabChangedListener(tabChangeListener);
}
private void addTab(TabHost tabHost, String tabSpec, String indicator, Drawable res, int content) {
tabHost.addTab(tabHost
.newTabSpec(tabSpec)
.setIndicator(indicator, res)
.setContent(content));
}
}``` As you can see I made the TabActivity into a RoboTabActivity and injected the 3 textViews and the resource. I also did an extract method to make it more readable.
Now I just have to get the listener out of there and prefereably inject it into our activity.
First I extract the Anonymous class we used for the OnTabChangedListener.
```java package be.baes;
import android.util.Log; import android.widget.TabHost;
public class LogTabChanged implements TabHost.OnTabChangeListener { @Override public void onTabChanged(String arg0) { Log.d(“cbaes”, “Tab was changed with arg” + arg0);
}
}``` Which leaves me with this in My TabViewActivity.
java
TabHost.OnTabChangeListener tabChangeListener = new LogTabChanged();
of course I would like to get rid of that new LogTabChanged() line and just inject it.
So the first thing I want to do is, is create a constructor where I will create such a class.
Something like this.
```java package be.baes;
import roboguice.activity.*; import roboguice.inject.InjectResource; import roboguice.inject.InjectView; import android.graphics.drawable.Drawable; import android.os.Bundle; import android.widget.TabHost; import android.widget.TextView;
public class TabViewActivity extends RoboTabActivity { @InjectResource(R.drawable.tab_one) Drawable tab_one_res; @InjectView(R.id.textView1) TextView textView1; @InjectView(R.id.textView2) TextView textView2; @InjectView(R.id.textView3) TextView textView3;
LogTabChanged logTabChanged;
public TabViewActivity()
{
logTabChanged = new LogTabChanged();
}
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
TabHost tabHost= this.getTabHost();
addTab(tabHost,"tab_test1","TAB 1",tab_one_res,textView1.getId());
addTab(tabHost,"tab_test2","TAB 2",tab_one_res,textView2.getId());
addTab(tabHost,"tab_test3","TAB 3",tab_one_res,textView3.getId());
tabHost.setCurrentTab(0);
TabHost.OnTabChangeListener tabChangeListener = logTabChanged;
tabHost.setOnTabChangedListener(tabChangeListener);
}
private void addTab(TabHost tabHost, String tabSpec, String indicator, Drawable res, int content) {
tabHost.addTab(tabHost
.newTabSpec(tabSpec)
.setIndicator(indicator, res)
.setContent(content));
}
}``` And now I like to have a constructor that accepts that as a parameter.
So first I will create an interface that I can inject that extands OnTabChangeListener.
<!– codeblock lang=““java” line=“1”package be.baes;
import android.widget.TabHost;
public interface ILogTabChanged extends TabHost.OnTabChangeListener { }
Then I make my listener implement that.
package be.baes; import android.util.Log;
public class LogTabChanged implements ILogTabChanged {
@Override public void onTabChanged(String arg0) { Log.d("cbaes", "Tab was changed with arg" + arg0); }}
And now I tell Guice which implementation it has to use for that interface.
package be.baes;
import roboguice.config.AbstractAndroidModule;
public class MyModule extends AbstractAndroidModule {
@Override
protected void configure() {
bind(ILogTabChanged.class).to(LogTabChanged.class);
}
}
And now I have to just inject it into my activity. I can’t use the constructor for this but I just inject it as a field.
And this is now what my Activity looks like.
package be.baes;
import com.google.inject.Inject;
import roboguice.activity.*;
import roboguice.inject.InjectResource;
import roboguice.inject.InjectView;
import android.graphics.drawable.Drawable;
import android.os.Bundle;
import android.widget.TabHost;
import android.widget.TextView;
public class TabViewActivity extends RoboTabActivity {
@InjectResource(R.drawable.tab_one) Drawable tab_one_res;
@InjectView(R.id.textView1) TextView textView1;
@InjectView(R.id.textView2) TextView textView2;
@InjectView(R.id.textView3) TextView textView3;
@Inject ILogTabChanged logTabChanged;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
TabHost tabHost= this.getTabHost();
addTab(tabHost,"tab_test1","TAB 1",tab_one_res,textView1.getId());
addTab(tabHost,"tab_test2","TAB 2",tab_one_res,textView2.getId());
addTab(tabHost,"tab_test3","TAB 3",tab_one_res,textView3.getId());
tabHost.setCurrentTab(0);
TabHost.OnTabChangeListener tabChangeListener = logTabChanged;
tabHost.setOnTabChangedListener(tabChangeListener);
}
private void addTab(TabHost tabHost, String tabSpec, String indicator, Drawable res, int content) {
tabHost.addTab(tabHost
.newTabSpec(tabSpec)
.setIndicator(indicator, res)
.setContent(content));
}
}
A whole lot cleaner then before, me thinks.
Conclusion
Using RoboGuice as your Ioc/Di container for your Android application is fairly easy. Documentation is however hard to find for RoboGuice all though it is not a new project and fairly well developed.
Chris is awesome.
