Android Studio第一个示例

第一个app

app示例

说明

主要设计layout布局，log cat日志，Toast日志

layout代码

activity_main.xml

<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"
    android:background="#C8FF00"
    android:padding="5dp">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_margin="30dp"
        android:background="#00FF90"
        android:orientation="vertical"
        android:padding="10dp"
        tools:ignore="Suspicious0dp">

        <TextView
            android:id="@+id/text_view"
            android:layout_width="match_parent"
            android:layout_height="0dp"
            android:text="I am a text"
            android:textColor="@color/black"
            android:textSize="30sp"
            android:layout_weight="1"
            android:gravity="center"
            android:layout_gravity="center_horizontal|center_vertical">
        </TextView>

        <Button
            android:id="@+id/button_view"
            android:layout_width="match_parent"
            android:layout_height="0dp"
            android:layout_weight="1"
            android:layout_gravity="center"
            android:text="btn1"
            android:textSize="30sp">
        </Button>

    </LinearLayout>

</LinearLayout>

java部分事件代码

MainActivity.java

package com.example.helloword2;

import androidx.appcompat.app.AppCompatActivity;

import android.graphics.Color;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button btn1 = findViewById(R.id.button_view);
        TextView text1 = findViewById(R.id.text_view);
        btn1.setOnClickListener(new MyBtnOneClickLisener());
    }

    class MyBtnOneClickLisener implements View.OnClickListener {
        @Override
        public void onClick(View v) {
            if (v.getId() == R.id.button_view) {
                TextView tx1 = findViewById(R.id.text_view);

                String tx1_text;
                tx1_text = (String) tx1.getText();

                if (tx1_text.equals("Hello,Ninghao!")) {
                    tx1.setText("I am a text");
                }

                if (tx1_text.equals("I am a text")) {
                    tx1.setText("Hello,Ninghao!");
                }

                String is_same = "False";

                Toast.makeText(MainActivity.this, is_same, Toast.LENGTH_SHORT).show();
                Log.d("tx1_text", tx1_text);

            }
        }
    }

}