@ZSCDumin 2019-07-10T11:41:03.000000Z 字数 7110 阅读 651

Android练习题

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">
    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />
</RelativeLayout>

第一步：

绑定控件(findViewById)

第二步：

给控件取值或者赋值(setText,getText)

第三步：

按钮点击事件

  button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                //此处写处理代码
            }
  });

异常

子线程更新UI出错，百度一下看看能不能自己解决

页面跳转

Intent intent =new Intent(当前Activity.this,目标Activity.class);
startActivity(intent);

带数据跳转需要用到：Bundle

ListView 的使用代码：

1、自定义适配器（里面要加载每一个列表子项的布局文件：item.xml）
2、给适配器加载数据
3、给ListView设置适配器

参考代码:

MaActivity.java

package com.zscdumin.test;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.widget.ListView;
import butterknife.Bind;
import butterknife.ButterKnife;
public class MainActivity extends AppCompatActivity {
    @Bind(R.id.listView)
    ListView listView;
    private int[] images = new int[1000];
    private String[] titles = new String[1000];
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        ButterKnife.bind(this);
        for (int i = 0; i < 1000; i++) {
            images[i] = R.drawable.icon;
            titles[i] = "item" + i;
        }
        MyAdapter myAdapter = new MyAdapter(this, R.layout.list_item, images, titles);
        listView.setAdapter(myAdapter);
    }
}

MyAdapter.java

package com.zscdumin.test;
import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Adapter;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.TextView;
public class MyAdapter extends BaseAdapter {
    private int[] images;
    private String[] titles;
    private Context context;
    private int resource;
    public MyAdapter(Context context, int resource, int[] images, String[] titles) {
        this.images = images;
        this.resource = resource;
        this.titles = titles;
        this.context = context;
    }
    @Override
    public int getCount() {
        return images.length;
    }
    @Override
    public Object getItem(int i) {
        return images[i];
    }
    @Override
    public long getItemId(int i) {
        return i;
    }
    @Override
    public View getView(int i, View view, ViewGroup viewGroup) {
        ViewHolder viewHolder;
        if (view == null) {
            viewHolder = new ViewHolder();
            view = LayoutInflater.from(context).inflate(resource, null);
            viewHolder.image = view.findViewById(R.id.imageView);
            viewHolder.title = view.findViewById(R.id.textView);
            view.setTag(viewHolder);
        } else {
            viewHolder = (ViewHolder) view.getTag();
        }
        viewHolder.image.setImageResource(images[i]);
        viewHolder.title.setText(titles[i]);
        return view;
    }
    final class ViewHolder {
        ImageView image;
        TextView title;
    }
}

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#d8e0e8"
    android:orientation="vertical">
    <ListView
        android:id="@+id/listView"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_weight="1" />
</LinearLayout>

list_item.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#d8e0e8"
    android:orientation="horizontal">
    <ImageView
        android:id="@+id/imageView"
        android:layout_width="50dp"
        android:layout_height="50dp"
        android:src="@mipmap/ic_launcher" />
    <TextView
        android:id="@+id/textView"
        android:layout_width="100dp"
        android:layout_height="50dp"
        android:layout_marginLeft="50dp"
        android:gravity="center"
        android:text="你好"
        android:textSize="20dp" />
</LinearLayout>

RecycleView 是在ListView基础之上做了优化

你们可以尝试一下往ListView添加10000行数据看看是否卡顿？

使用步骤：