这是一个界面

代码如下：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
   android:orientation="vertical"
    tools:context="com.example.administrator.myapplication.MainActivity">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello World!"
        android:id="@+id/textView" />

    <EditText
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:inputType="textPersonName"
        android:hint="enter your name here"
        android:ems="10"
        android:id="@+id/editText" />

    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="SAY HELLO!"
        android:id="@+id/btn1" />
</LinearLayout>

 主代码：

package com.example.administrator.myapplication;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.EditText;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {
  private TextView textView;
    private EditText editText;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }
    public void sayHello(View view){
        TextView textView=(TextView)findViewById(R.id.textView);
        EditText editText=(EditText)findViewById(R.id.editText);
        textView.setText("Hello,"+editText.getText().toString()+"!");
    }
}

测试代码：

package com.example.administrator.myapplication;

import android.support.test.rule.ActivityTestRule;

import org.junit.Rule;
import org.junit.Test;

import static android.support.test.espresso.Espresso.onView;
import static android.support.test.espresso.action.ViewActions.typeText;
import static org.junit.Assert.*;

/**
 * Created by Administrator on 2017/3/16.
 */
public class MainActivityTest {
    @Rule
    public ActivityTestRule<MainActivity>mActivityRule=new ActivityTestRule<>(MainActivity.class);
    @Test
    public void testSayHello() throws Exception {
        onView(withId(R.id.editText)).perform(typeText(STRING_TO_BE_TYPED).closeSoftKeyboard());

        onView(withId(R.id.btn)).perform(click());
        String expectedText="Hello,"+STRING_TO_BE_TYPED+"!";
        onView(withId(R.id.textview)).check(matches(withText(expectedText)));

    }
}
build代码:

package com.example.administrator.myapplication;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.EditText;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {
  private TextView textView;
    private EditText editText;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }
    public void sayHello(View view){
        TextView textView=(TextView)findViewById(R.id.textView);
        EditText editText=(EditText)findViewById(R.id.editText);
        textView.setText("Hello,"+editText.getText().toString()+"!");
    }
}

代码作业