调用系统相机拍照并保存在sdcard上

    public void click(View view) throws Exception {
        Intent intent = new Intent();
        intent.setAction("android.media.action.IMAGE_CAPTURE");
        intent.addCategory("android.intent.category.DEFAULT");
        String fileName = new SimpleDateFormat("yyyyMMdd_HHmmss").format(new Date())+".jpg";
        System.out.println(fileName);
        File file = new File("/sdcard/"+fileName);
        intent.putExtra(MediaStore.EXTRA_OUTPUT, Uri.fromFile(file));
        startActivity(intent);
    }

    <uses-permission android:name="android.permission.CAMERA"></uses-permission>
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
    <!--<uses-feature android:name="android.hardware.camera"/>-->

 另：

import android.content.Intent;
import android.net.Uri;
import android.os.Environment;
import android.os.SystemClock;
import android.provider.MediaStore;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;

import java.io.File;

public class MainActivity extends AppCompatActivity {
    private Button btn1;
    private String TAG = "log";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        btn1 = (Button) findViewById(R.id.btn1);
        final File file = new File(Environment.getExternalStorageDirectory(), SystemClock.uptimeMillis()+".jpg");

        btn1.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
                intent.putExtra(MediaStore.EXTRA_OUTPUT, Uri.fromFile(file));
                startActivityForResult(intent,200);
            }
        });
}

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        if (requestCode == 200) {

        }
        Log.i(TAG, "onActivityResult: "+ requestCode + " " + resultCode);
        super.onActivityResult(requestCode, resultCode, data);
    }
}