接着处理《Android 网络图片查看器》中出现的问题
使用添加子线程，修改原程序：
package com.wuyudong.imagesviewer;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import org.apache.http.HttpConnection;
import android.os.Bundle;
import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.text.TextUtils;
import android.view.Menu;
import android.view.View;
import android.widget.EditText;
import android.widget.ImageView;
import android.widget.Toast;
public class MainActivity extends Activity {
private EditText et_path;
private ImageView iv;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
et_path = (EditText) findViewById(R.id.et_path);
iv = (ImageView) findViewById(R.id.iv);
}
public void click(View view) {
final String path = et_path.getText().toString().trim();
if (TextUtils.isEmpty(path)) {
Toast.makeText(this, "图片路径不能为空", 0).show();
} else {
new Thread() {
@Override
public void run() {
// 连接服务器get请求获取图片
try {
URL url = new URL(path);
// 根据url发送http的请求
HttpURLConnection conn = (HttpURLConnection) url
.openConnection();
// 设置请求的方式
conn.setRequestMethod("GET");
conn.setConnectTimeout(5000);
conn.setReadTimeout(5000);
conn.setRequestProperty(
"User-Agent",
"Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/45.0.2454.101 Safari/537.36");
int code = conn.getResponseCode();
if (code == 200) {
InputStream is = conn.getInputStream();
Bitmap bitmap = BitmapFactory.decodeStream(is);
iv.setImageBitmap(bitmap);
} else {
Toast.makeText(MainActivity.this, "显示图片失败", 0)
.show();
}
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
Toast.makeText(MainActivity.this, "访问获取图片失败", 0).show();
}
}
}.start();
}
}
}
运行项目后报错：
06-27 19:27:59.613: W/System.err(2471): android.view.ViewRootImpl$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views.
谁创建了view对象，谁才能动修改view。
代码：iv.setImageBitmap(bitmap);目的就是为了修改UI
也即是主线程才可以修改。为了控制多线程修改view同步问题而设定的
修改后的代码如下:
package com.wuyudong.imagesviewer;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import org.apache.http.HttpConnection;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.text.TextUtils;
import android.view.Menu;
import android.view.View;
import android.widget.EditText;
import android.widget.ImageView;
import android.widget.Toast;
public class MainActivity extends Activity {
protected static final int CHANGE_UI = 1;
protected static final int ERROR = 2;
private EditText et_path;
private ImageView iv;
// 1、主线程创建消息处理器
private Handler handler = new Handler() {
public void handleMessage(android.os.Message msg) {
if (msg.what == CHANGE_UI) {
Bitmap bitmap = (Bitmap) msg.obj;
iv.setImageBitmap(bitmap);
} else if (msg.what == ERROR) {
Toast.makeText(MainActivity.this, "访问获取图片失败", 0).show();
}
};
};
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
et_path = (EditText) findViewById(R.id.et_path);
iv = (ImageView) findViewById(R.id.iv);
}
public void click(View view) {
final String path = et_path.getText().toString().trim();
if (TextUtils.isEmpty(path)) {
Toast.makeText(this, "图片路径不能为空", 0).show();
} else {
new Thread() {
@Override
public void run() {
// 连接服务器get请求获取图片
try {
URL url = new URL(path);
// 根据url发送http的请求
HttpURLConnection conn = (HttpURLConnection) url
.openConnection();
// 设置请求的方式
conn.setRequestMethod("GET");
conn.setConnectTimeout(5000);
conn.setReadTimeout(5000);
conn.setRequestProperty(
"User-Agent",
"Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/45.0.2454.101 Safari/537.36");
// 得到服务器返回的响应码
int code = conn.getResponseCode();
if (code == 200) {
InputStream is = conn.getInputStream();
Bitmap bitmap = BitmapFactory.decodeStream(is);
// iv.setImageBitmap(bitmap);
// TODO:告诉主线程一个消息：帮我更改界面，内容：bitmap
Message msg = new Message();
msg.what = CHANGE_UI;
msg.obj = bitmap;
handler.sendMessage(msg);
} else {
// Toast.makeText(MainActivity.this, "显示图片失败", 0)
// .show();
Message msg = new Message();
msg.what = ERROR;
handler.sendMessage(msg);
}
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
// Toast.makeText(MainActivity.this, "访问获取图片失败",
// 0).show();
Message msg = new Message();
msg.what = ERROR;
handler.sendMessage(msg);
}
}
}.start();
}
}
}
时间： 2024-10-27 13:33:33