Android Studio 之 控件基础知识

1. TextView 和 EditText 控件常用属性 

android:layout_width="match_parent"        宽度与父控件一样宽
android:layout_height="wrap_content"       包裹内容
android:layout_marginStart="8dp"           左外边距8dp
android:layout_marginEnd="8dp"             右外边距8dp
android:background="#FFFFFF"               背景色
android:ems="10"
android:gravity="top"                      文字对齐
android:hint="说点什么吧..."
android:inputType="textMultiLine"          多行输入
android:lines="6"                          显示行数
android:padding="5dp"                      内边距

android:drawableStart="@drawable/addpicture"  在编辑框放一个图片

 2.Button 的 onClick 事件

另一个办法，在代码中创建按钮的事件监听器

Button button = findViewById(R.id.button);
        //给按钮创建[事件监听器]
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Toast.makeText(MainActivity.this,"单击了按钮",Toast.LENGTH_SHORT).show();
            }
        });

　　

 3.按钮上设置 xml 背景

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle">
    <solid android:color="#1FBAF3"></solid>
    <corners android:radius="5dp"></corners>
    <padding
        android:bottom="10dp"
        android:left="15dp"
        android:right="15dp"
        android:top="10dp"
        ></padding>
</shape>

按钮属性加上： android:background="@layout/shape"

4.图片按钮

android:background="#0000"  背景透明

5.Activity 的切换

Intent intent = new Intent(MainActivity.this,Main2Activity.class);
startActivity(intent);
finish();  //关闭Activity,返回到打开它的窗口， 如果是启动窗口调用finish()，则直接退出程序

onCreate(null); //刷新窗口 

直接修改启动窗口，在清单文件中修改，将 Main2Activity 修改成 其他Activity，就会从其他窗口先启动，入口 Activity

<activity android:name=".Main2Activity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>

　　

6.Activity 之间数据传递 (Bundle   Intent)

窗口1代码：

Button button = findViewById(R.id.buttonBunldIntent);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String name = ((EditText)(findViewById(R.id.editTextUserName))).getText().toString().trim();
                String pwd = ((EditText)findViewById(R.id.editTextPasword)).getText().toString().trim();
                String mobile = ((EditText)findViewById(R.id.editTextMobile)).getText().toString().trim();
                if(name=="" || pwd=="" || mobile =="" ){
                    Toast.makeText(BundleIntentActivity.this,"用户名、密码、手机号 三者输入不完整！",Toast.LENGTH_SHORT);
                    return;
                }
                Intent intent = new Intent(BundleIntentActivity.this,BundleIntentActivity2.class);
                Bundle bundle = new Bundle();
                bundle.putCharSequence("name",name);
                bundle.putString("pwd",pwd);
                bundle.putString("mobile",mobile);
                intent.putExtras(bundle);
                startActivity(intent);

            }
        });

　　

窗口2代码：

Intent intent = getIntent();
        Bundle bundle = intent.getExtras();
        String name = bundle.getString("name");
        String mobile = bundle.getString("mobile");
        String pwd = bundle.getString("pwd");

        TextView  tv = findViewById(R.id.textViewInfo);
        tv.setText("name=" + name + "\n" + "pwd=" + pwd + "\nmobile=" + mobile);

　　

6.Activity 返回数据 

界面2，通过gridView 显示头像

第1个界面，通过 startActivityForResult(intent) 跳到第2个界面，通过事件onActivityResult接收返回的数据

第2个界面，setResult(0x11,intent) 返回数据

界面1代码：

protected void onCreate(Bundle savedInstanceState) {

//选择头像
        findViewById(R.id.buttonSelHead).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent(MainActivity.this,SelHeadActivity.class);
                startActivityForResult(intent,0x11);
            }
        });

}

//返回数据显示到图片控件上
@Override
    protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        if(requestCode == 0x11 && resultCode == 0x11){
            Bundle bundle = data.getExtras();
            int imageId = bundle.getInt("imageId");
            ImageView imageView = findViewById(R.id.imageView);
            imageView.setImageResource(imageId);
        }
    }

　　

界面2代码：

package com.example;

import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.view.ViewGroup;
import android.view.WindowManager;
import android.widget.AdapterView;
import android.widget.BaseAdapter;
import android.widget.GridView;
import android.widget.ImageView;

import androidx.appcompat.app.AppCompatActivity;

public class SelHeadActivity extends AppCompatActivity {

    //定义头像数组
    public int[] imageId = new int[]{R.drawable.tx1,R.drawable.tx2,R.drawable.tx3,R.drawable.tx4,R.drawable.tx5,R.drawable.tx6,R.drawable.tx7,R.drawable.tx8};

    @Override
    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_sel_head);

        GridView gridView = findViewById(R.id.gridViewHead);
        BaseAdapter adapter = new BaseAdapter() {
            @Override
            public int getCount() {
                return imageId.length;
            }

            @Override
            public Object getItem(int position) {
                return position;
            }

            @Override
            public long getItemId(int position) {
                return position;
            }

            @Override
            public View getView(int position, View convertView, ViewGroup parent) {
                ImageView imageView;

                //获取屏幕宽度
                //获取窗口管理器
                WindowManager wm = getWindowManager();
                int width = wm.getDefaultDisplay().getWidth();
                int ImageWidth = width/4-10;

                if(convertView == null){
                    imageView = new ImageView(SelHeadActivity.this);
                    imageView.setAdjustViewBounds(true);
                    imageView.setMaxHeight(ImageWidth);
                    imageView.setMaxWidth(ImageWidth);
                    imageView.setPadding(5,5,5,5);
                }
                else{
                    imageView = (ImageView) convertView;
                }
                imageView.setImageResource(imageId[position]);

                return imageView;
            }
        };

        gridView.setAdapter(adapter);

        gridView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                Intent intent = getIntent();
                Bundle bundle = new Bundle();
                bundle.putInt("imageId",imageId[position]); //实例化要传递的数据包
                intent.putExtras(bundle);         //将数据包保存到 intent 中
                setResult(0x11,intent); //设置返回的结果码
                finish();   //关闭当前Activity
            }
        });

    }
}

图片放在gridView 控件中

　　

 7. Dialog 提示框 

AlertDialog.Builder builder = new AlertDialog.Builder(MainActivity.this);
builder.setMessage("回答错误，下面请看解析：当张山");
builder.setPositiveButton("确定",null ).show();

　　

8. android:layout_margin 与 padding

android:layout_margin 外边距

padding 内边距

9.设置成横屏显示

10.ImageView

adjustViewBounds 保持宽高比

hint 图片着色

scaleType 缩放类型

11. ImageSwitcher 图片切换器

package com.example;

import android.os.Bundle;
import android.view.MotionEvent;
import android.view.View;
import android.view.Window;
import android.view.WindowManager;
import android.view.animation.AnimationUtils;
import android.widget.ImageSwitcher;
import android.widget.ImageView;
import android.widget.ViewSwitcher;

import androidx.appcompat.app.AppCompatActivity;

public class ImageSwitchTest2 extends AppCompatActivity {

    private int[] arrayPictures={R.drawable.tx1,R.drawable.tx2,R.drawable.tx3,R.drawable.tx4,R.drawable.tx5,R.drawable.tx6,R.drawable.tx7,R.drawable.tx8};

    private ImageSwitcher imageSwitcher;
    private int index;
    private float touchDownX;
    private float touchUpX;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_image_switch_test2);

        //设置全屏
        Window window = getWindow();
        WindowManager.LayoutParams winParams = window.getAttributes();
        winParams.flags=WindowManager.LayoutParams.FLAG_FULLSCREEN;
        window.setFlags(winParams.flags,winParams.flags);

        imageSwitcher = findViewById(R.id.imageSwitcher1);
        imageSwitcher.setFactory(new ViewSwitcher.ViewFactory() {
            @Override
            public View makeView() {
                ImageView imageView = new ImageView(ImageSwitchTest2.this);
                imageView.setImageResource(arrayPictures[index]);
                imageView.setMinimumWidth(200);
                imageView.setMinimumHeight(200);
                return imageView;
            }
        });

        imageSwitcher.setOnTouchListener(new View.OnTouchListener() {
            @Override
            public boolean onTouch(View v, MotionEvent event) {
                if(event.getAction() == MotionEvent.ACTION_DOWN){
                    touchDownX = event.getX();
                    return true;
                }
                else if(event.getAction() == MotionEvent.ACTION_UP){
                    touchUpX = event.getX();
                    //从左到右
                    if(touchUpX - touchDownX>100){
                        index = (index == 0 ? arrayPictures.length-1:index-1);

                        //设置动画资源
                        imageSwitcher.setInAnimation(AnimationUtils.loadAnimation(ImageSwitchTest2.this,R.anim.slide_in_right));
                        imageSwitcher.setOutAnimation(AnimationUtils.loadAnimation(ImageSwitchTest2.this,R.anim.slide_out_right));

                        imageSwitcher.setMinimumWidth(200);
                        imageSwitcher.setMinimumHeight(200);
                        imageSwitcher.setImageResource(arrayPictures[index]);

                    }
                    //从右到左
                    else if(touchDownX - touchUpX > 100){
                        index = (index == arrayPictures.length ? arrayPictures.length-1:index+1);

                        //设置动画资源
                        imageSwitcher.setInAnimation(AnimationUtils.loadAnimation(ImageSwitchTest2.this,R.anim.slide_in_left));
                        imageSwitcher.setOutAnimation(AnimationUtils.loadAnimation(ImageSwitchTest2.this,R.anim.slide_out_left));

                        imageSwitcher.setMinimumWidth(200);
                        imageSwitcher.setMinimumHeight(200);
                        imageSwitcher.setImageResource(arrayPictures[index]);
                    }
                }

                return true;
            }
        });

    }
}